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TRANSACTIONS 



OF THE 



EOYAL SOCIETY OF EDINBUKGH. 

VOL. XXXVIII. PART I.— FOR THE SESSION 1894-95. 



CONTENTS. 



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Page 
I. The Clyde Sea Area. By Hugh Kobert Mill, D.Sc, F.R.S.E. (Plates T.-XXXII.) 

Part ni. — Distribution of Temperature, ...... 1 

(Issued separately, November \Wi, 1894.) 

II. A Fundamental Theorem regarding the Equivalence of Systems of Ordinary Linear Differ- 
ential Equations, and its Application to the Determination of the Order and the 
Systematic Solution of a Determinate System of such Equations. By George 
Chrystal M.A. LL.D., Professor of Mathematics in the University of Edinburgh, . 163 
(Issued separately, May 5th, 1895.) 

III. On Bird and Beast in Ancient Symbolism. By Professor D'Arcy Wentworth 

Thompson, Jr., . . . . . . . . .179 

(Issued separately, August 3rd, 1895.) 

IV. Two Olens and tht Agency of Glaciation. By His Grace The Duke of Argyll, 

K.G., K.T. (V 'th a Map), . 193 

(Issued separately, September '20th, 1895.) 

V. On the Fossil Flora the Yorkshire Coal Field. (First Paper.) By Robert Kidston, 

F.R.S.E., F.G.S. (Plates I.-III.), 203 

■Issued separately, February 5th, 1896.) 

VI. Experiments on the Transcirse Effect and on some Related Actions in Bismuth. By 

J. C. Beattie. (With a Plate), . . . . . . .225 

(Issued separately, October 10th, 1895.) 

VII. On the Relation between the Variation of Resistance in Bismuth in a Steady Magnetic Field 

and the Rotatory or Transverse Effect. By J. C. Beattie. (With a Plate), . . 241 

(Issued separately, December 7th, 1895.) 



EDINBURGH: 

PUBLISHED BY ROBERT GRANT & SON ; 107 PRINCES STREET, 
AND WILLIAMS & NORGATE, 14 HENRIETTA STREET, COVENT GARDEN, LONDON. 



MDCCCXC 
Price Two Pouvds. 



TRANSACTIONS 



OF THK 



ROYAL SOCIETY OF EDINBURGH. 



S. Or C3f> 



TRANSACTIONS 



OF THE 



ROYAL SOCIETY 



OK 



EDINBURGH. 



VOL. XXXVIII. 




EDINBURGH: 

PUBLISHED BY ROBERT GRANT & SON, 107 PRINCES STREET. 
AND WILLIAMS & NORGATE, 14 HENRIETTA STREET, COVENT GARDEN, LONDON, 



MDCCCXCVII. 



No. 



I. 
II. 
III. 
IV. 
V. 
VI. 
VII. 
VIII. 
IX. 
X. 
XI. 
XII. 



Published 



November 13, 1894. 
May 5, 1895. 
August 3, 1895. 
September 20, 1895. 
February 5, 1896. 

October 10, 1895. 

December 7, 1895. 

December 9, 1895. 

January 15, 1896. 

.lanuary 10, 1896. 

February 4, 1896. 

February 2, 1896. 



No. 



XIII. 


Published 


XIV. 


j> 


XV. 


)> 


XVI. 


sj 


XVII. 


)> 


XVIII. 


)> 


XIX. 


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XX. 


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XXI. 


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XXII. 


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XXIII. 


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XXIV. 


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April 21, 1896. 
June 12, 1896. 
July 17, 1896. 
September 11, 1896. 
September 10, 1896. 

August 12, 1896. 
September 1, 1896. 

October 12, 1896. 

October 19, 1896. 

November 25, 1896. 

October 26, 1896. 

November 16, 1896. 



CONTENTS. 



PAKT I. (1894-96.) 

NUMBER PAGE 

I. The Clyde Sea Area. By Hugh Robert Mill, I). 8c, F.R.S.E. 

Part III. — Distribution of Temperature. (With Thirty-two Plates), 1 

II. A Fundamental Theorem regarding the Equivalence of Systems of 
Ordinary Linear Differential Equations, and its Application to the 
Determination of the Order and the Systematic Solution of a Deter- 
minate System of such Equations. By George Chrystal, M.A., 
LL.D., Professor of Mathematics in the University of Edinburgh, . 163 

III. On Bird and Beast in Ancient Symbolism. By Professor D'Arcy 

Wentworth Thompson, Jr., . . . . . .179 

IV. Two Glens and the Agency of Glaciation. By His Grace The Duke 

of Argyll, K.G., K.T. (With a Map), . . . .193 

V. On the Fossil Flora of the Yorkshire Coal Field. (First Paper.) By 

Robert Kidston, F.R.S.E., F.G.S. (With Three Plates), . . 203 

VI. Experiments on the Transverse Effect and on some Related Actions in 

Bismuth. By J. C. Beattie. (With a Plate), . . . 225 

VII. On the Relation between the Variation of Resistance in Bismuth in a 
Steady Magnetic Field and the Rotatory or Transverse Effect. By J. 
C. Beattie. (With a Plate), . . . . . .241 



VI CONTENTS. 



PART II. (1895-90.) 

M'MHHR PAGE 

VIII. On the Comparative Histology and Physiology of the Spleen. By A. J. 

Whiting, M.D. (With Three Plates), .... 253 

IX. Specific Gravities and Oceanic Circulation. By Alex. Buchan, M.A., 



LL.D. (With Nine Maps) ...... 31 



PART III. (1896.) 



X. On the Deep and Shallow-water Marine Fauna of the Kerguelen Region 
of the Great Southern Ocean. By John Murray, D.Sc, LL.D., 
Ph.D., of the Challenger Expedition. (With a Map), . . 343 

XI. On a Case of Colour Blindness. By Wm. Peddie, D.Sc. Part I. (With 

a Plate), ........ 501 



XII. The Development of the Mullerian Duct of Amphibians. By Gregg 

Wilson, M.A., B.Sc, Edin. (With Two Plates.) Communicated by 

Prof. Cossar Ewart, M.D., F.R.S., . . . . .509 

XIII. The Strains Produced in Iron, Steel, and Nickel Tubes in the Magnetic 

Field. Part I. By Professor C G. Knott, D.Sc, F.R.S.E. 
(With Six Plates), ....... 527 

XIV. A Revised Description of the Dorsal Interosseous Muscles of the Human 

Hand, with Suggestions for a New Nomenclature of the Palmar 
Interosseous Muscles, and, some Observations on the Corresponding 
Muscles in the Anthropoid Apes. By David Heprurn, M.D., CM., 
F.R.S.E., Lecturer on Regional Anatomy in the University of 
Edinburgh. (With a Plate), . . . . . .557 

XV. The Temperature Variation of the Magnetic Permeability of Magnetite. 

By Edwin J I. Barton, D.Sc. (Lond.), F.R.S.E., A.I.E.E., Senior 
Lecturer and Demonstrator in Physics at University College, 
Nottingham. (With Three Plates), . . . . .507 



CONTENTS. vii 

KHMBEH PAGE 

XVI. The Weather, Influenza, and Disease : from the Records of the Edin- 
burgh Royal Infirmary for Fifty Years. By A. Lockhart Gil- 
lespie, M.D., F.R.C.P.E. ; Memb. Scot. Met. Soc. ; Medical 
Registrar, Edinburgh Royal Infirmary. (With Six Plates), . 579 

XVII. The ?' of Dioph mitus. By Prof. D'Arcy Wentworth Thompson, . 607 

XVIII. On Torsional Oscillations of Wires. By Dr W. Peddie. (With Two 

Plates), ........ 611 

[7 XIX. On the Cranial Ner ves of Chimaera Monstrosa (Linn. 1754): with a 
Discussion of the lateral Line System, and of the Morphology of the 
Chorda tympani. By Frank J. Cole, Demonstrator and Assistant 
Lecturer of Zoology, University College, Liverpool. Communicated 
by Professor Ewart, M;D., F.R.S. (With Two Plates), . . 631 

XX. The Meteorology of Edinburgh. By Robert Cockburn Mossman, 

F.R.S.E., F.R.Met.Soc. (With Three Plates), . . .681 

XXI. On the Curves of Magnetisation for Films of Iron, Cobalt, and Nickel. 

By Dr J. C. Bkattie. (With a Plate), .... 757 



PART IV. (1896.) 

XXII. Observations on the Phonograph. By John G. M'Kendrick, M.D., 
Professor of Physiology in the University of Glasgow. (Witb Two 
Plates), . . . . . . . .765 

XXIII. On the Genus Anaspides and its Affinities with certain Fossil Crustacea. 

By W. T. Calman, B.Sc, University College, Dundee. Communi- 
cated by Professor D'Arcy W. Thompson. (With Two Plates), . 787 

XXIV. On the ^-discriminant of a Differential Equation of the First Order, 

and on Certain Points in the General Theory of Envelopes connected 
therewith. By Professor Chrystal, . . . .803 



\ 111 



CONTENTS 



AlM'KNDIX 



The Council of Society, . 

Alphabetical List of the* Ordinary Fellow*, 



List of Honorary Fellow* at March 1897, 



List of Ordinary Fellow* Elected during Session 1894-95, 
Fellows Deceased or Resigned, 1894-95, . 
List of Ordinary Fellows Elected during Session 1895-96, 
Fellows I ')cceasea lor Resigned, 1895-96, . 



Laws of the Society, 



829 
831 
847 
849 
850 
851 
852 
853 



The Keith, Makdoug all-Brisbane, Neill, and Gunning Victoria Jubilee 

Prize*, ........ 860 

Awards of the Keith, Makdougall- Brisbane, Neill, and Gunning Victoria 

Jubilee Prizes, from. 1827 to 1896, . . . . .863 



Proceedings of the Statutory General Meetings, 1894 and 1895, . 



869 



List of Public Institutions and Individuals entitled to receive Copies of 

the Transactions and Proceedings of the Royal Society, . . 875 



Index, 



882 



;A 



25 JAN 







TKANSACTIONS, 



L— The Clyde Sea Area. By Hugh Robert Mill, D.Sc, F.R.S.E. (Plates I.-XXXII.) 

Part III. — Distribution of Temperature. 

(Read June 19, 1893.) 

Preliminary. 

The first two parts of this paper — Physical Geography and Salinity — were 
communicated to the Society on May 18th, 1891, and published in the Transactions, 
Vol. XXXVL, Part III., No. 23, pp. 641-729. 

Various circumstances have prevented me from sooner presenting the concluding 
part of the discussion. I postponed publication again and again, in the hope that 
it might be possible to discuss the results more thoroughly, and deduce from them 
more clearly than I have been able to do the laws which regulate the heat-transactions 
of sea-water of varying salinity, contained in basins of differing degrees of isolation 
from the circulation of the ocean. At length the conclusion has been arrived at that 
the observations are not sufficiently uniform, regular, and close to warrant the expendi- 
ture of the time devoted to their discussion. Many months of work have been 
occupied in proving that some special manner of classifying and treating the data led 
to no definite result. Thus, it is unnecessary to describe several series of voluminous 
calculations, or to bring forward a great number of maps and sections on which the 
distribution of temperature was plotted in different ways. It is difficult to establish 
theoretical conclusions of a general and far-reaching kind from my work, and I have 
not attempted to compare it with the many memoirs published in continental journals, 
on the temperature of lakes, fjords, and enclosed seas. During the last few years it has 
only been possible for me to discuss the results in spare hours, snatched from the 
engrossing occupations of University Extension lecturing, and literary work in other 
departments of science, so that I have never been able to master simultaneously the 
crowd of details, but obliged to treat each unit of the work separately, returning to it 
often after weeks in which the earlier discussions had been partly forgotten. Thus the 

-VOL. XXXVIII. PART I. (NO. 1). A 



2 DR HUGH ROBERT MILL ON THE 

memoir is, in large measure, a patchwork or agglomeration of minor discussions, the 
result of the attempt to do a piece of original work in physical geography in a country 
where there is scant recognition in the Universities of such special study or research. 
I must, however, record my indebtedness to the temporary Elective Fellowship in 
Experimental Physics in the University of Edinburgh, which enabled me to devote two 
years exclusively to the practical work of carrying out observations, and to the 
Government Grant Committee for sums of money which sufficed to pay for such 
additional assistance as" was required in carrying out the discussion. Without such help, 
the work would have been impossible. Any value it now possesses lies in the fact 
that it is a presentation of actual observations made at the same stations, with the 
utmost care, and by precisely the same methods, although at somewhat irregular 
intervals of time, for three and a half years. These observations were published partly 
in the Journal of the Scottish Meteorological Society * and partly in the Proceedings 
of this Society. t Here they are arranged in the manner which, after repeated trials, 
seems to be that best adapted to bring out their characteristic features: in some 
aspects they are generalised, and in every case, as far as possible, brought into 
connection with the related tidal or climatic phenomena. 

One of the most instructive results is that the omission of one or two sets of observa- 
tions would give an entirely different complexion to the whole series. Not only might 
the date of a seasonal maximum or minimum be missed in this way, but the sudden and 
profound disturbances of seasonal changes, which are otherwise apparently uniform, 
would pass undetected. These irregular changes make it doubtful whether any one year 
can be fairly compared with any other. The determining conditions of temperature-change 
are much more numerous and complicated than was suspected from the preliminary 
discussions made while the observations were in progress.^ Thus it now appears 
that it is necessary to know the direction and force of the wind, not only at the 
time when the observations were made, but every day during the whole period of 
observation. And since the direction of the wind is modified by the configuration 
of the land around each loch, it is impossible to arrive at the actual directions from 
a study of the weather-charts. There are practically no meteorological stations in 
the landward division of the Area, so that no contemporary observations of wind are 
available. These limitations have been carefully kept in view, and I have endeavoured 
to carry each train of reasoning no farther than is justified by the ascertained facts. 

It was originally my ambition to calculate out the total changes of heat for the 
whole Clyde Sea Area looked upon as a closed system ; but after working long at the 
problem I was obliged to abandon it on account of the small number of observations in 
the seaward part, and the unknown influence of the wide margin of shallow water along the 
Ayrshire coast. A fairly good guess may be made of the total amount of heat at the time 

• Journ. Scot. Met. Soc, 3rd ser. (1886), vol. vii., No. 3, pp. 313-351 (1887), vol. viii., No. 4, pp. 47-110. 

+ I'roc. Rmj. Soc. Edin., vol. xviii., pp. 139-228. 

t Physical Conditions of the Water in the Clyde Sea Area, Proc. Glasgow Phil. Soc, vol. xviii. (1887), pp. 332-356. 



CLYDE SEA AEEA. 3 

of the annual minimum, when the temperature appears to become uniform both in regional 
and bathymetrical distribution. At other times, however, it was only found possible to 
estimate the heat-content of the water in small and well-defined natural regions. 

In presenting this paper, I have to express my thanks to many, friends and fellow- 
workers for advice and assistance. Dr John Murray, who initiated and directed the 
whole work, has, at various stages, given the most helpful suggestions, and the observa- 
tions made in the later trips of the "Medusa" were done entirely under his supervision 
or by himself personally. Mr J. Y. Buchanan, F.R.S., kindly gave the use of his 
observations on Loch Lomond, for comparison with those on the lochs of the Clyde 
Sea Area. Mr A. J. Herbertson and Mr E. Turnbull drew all the curves of vertical 
distribution of temperature for each station ; Dr W. Peddie estimated the mean 
temperature of each of the curves ; while Mr H. N. Dickson estimated the mean 
temperature of the various loch-basins from the vertical sections, and rendered other 
help. 

Instruments and Methods. 

Surface Temperature. — The temperature of the surface water was observed in 
two different ways, which gave practically identical results. When a serial temperature- 
sounding was made, the Negretti and Zambra reversing thermometer was employed, the 
frame of the instrument being just immersed, so that the bulb was about six inches below 
the surface. On other occasions, when it was desirable to obtain the surface temperature 
without stopping the vessel, a bucketful of surface water was taken on board, and a 
mercurial thermometer, with large bulb and stem divided into degrees Fahrenheit, 
immersed in it. The bucket was placed in the shade, and the thermometer left in 
it for about two minutes, being used to stir the water thoroughly before it was 
read. Care was always taken to draw the sample of water well forward in the vessel, 
so that there could be no possibility of admixture of warm water from the condenser 
or any discharge-pipe. The error of the surface thermometer was carefully ascertained, 
at intervals of a few months, by comparison with a standard thermometer. 

Deep-Sea Thermometer. — For observations beneath the surface the instrument exclu- 
sively employed was Negretti and Zambra's Patent Standard Deep-Sea Thermometer. 
All thermometers used were graduated on the Fahrenheit scale, which presents many 
advantages for observational purposes, and all temperatures are given on that scale. The 
principle of the thermometer is well known. It is in fact an out-flow thermometer, in 
which the mercury that escapes from the bulb is measured instead of being weighed. 
There is a constriction in the stem just above the bulb, and then the bore is enlarged into 
a small lateral pouch or chamber. In an upright position the thermometer acts like any 
other, but when it is inverted the mercury column breaks off at the constriction and runs 
into the tube, which is graduated in degrees so as to be read in the inverted position. 
The whole thermometer is sealed up in a strong glass tube to protect it against pressure, 
and the bulb is surrounded with mercury to transmit the heat rapidly. 

After the thermometer is inverted, the record of the temperature remains unchanged, 



4 DR HUGH ROBERT MILL ON THE 

except for the slight expansion or contraction of the broken-off column by change of 
temperature. I made a series of experiments on the temperature correction of eight of 
these thermometers, and found, as the average of many trials, that a change of 
60° F. lengthened the broken-off column by 1° of the scale, the temperatures 
employed being 32° and 92°. Hence for a change of 6° between the temperature 
of reversing and that of reading, a correction of one-tenth should apparently be 
applied. In summer, for instance, a thermometer reversed at 45°, hauled up rapidly, 
and read in air at 65°, might appear to require a correction of o, 3 ; but, recollect- 
ing that the thermometer is read before it has time to assume the temperature 
of the air, and that it is wet, we see that the amount of correction should be 
considerably less. If the thermometer is hung up in the wind for five minutes, and kept 
wet all the time (for it would be impossible to dry it thoroughly), the wet bulb tempera- 
ture of the air, ascertained by a sling thermometer, might be used to correct the readings. 
Or, more simply, the inverted thermometer may be placed for a few minutes, before read- 
ing it, in a bucket of surface water, the temperature of which can easily be noted, and the 
corresponding correction applied. This was done on several occasions when the difference 
of temperature between water and air was over 10°, — a state of matters which rarely occurred 
in the Clyde Sea Area, except for the bottom temperatures of Loch Fyne and Loch Goil 
in summer. A simpler method, subsequently adopted, was to read the thermometer as it 
came up, then right it sharply, and immediately reverse again, the second reading giving 
the exact temperature of the instrument at which the first reading was made. In prepar- 
ing the results for publication it was not found necessary to apply this special correction. 
The thermometers acquired a considerable index error in the time during which they 
were used : in one case it amounted to as much as 0°'5. This error was determined periodi- 
cally by the use of melting ice, and of water at a higher temperature in which a standard 
thermometer was immersed. In calm weather, and by the use of ordinary precautions to 
insure correct readings, the observations could be trusted to o- l F. Although well suited 
for work in a climate like that of the West of Scotland, in most of the thermometers I 
have examined the pouch-shaped recess is not large enough to contain the overflow from 
the bulb when the temperature is raised 60° or more after inversion ; and in other cases, 
although the pouch is large enough to hold the overflow, a very slight jerk is sufficient to 
carry it past the siphon bend, and so vitiate the record. The bulb of the thermometer 
being filled with mercury and surrounded by it, very rapidly accommodates itself to the 
temperature of the water in which it is immersed. From experiments made at different 
times it appears that in ordinary circumstances less than a minute suffices ; but when the 
difference of temperature exceeds 5° two minutes may be necessary. In order to make 
perfectly sure of equilibrium of temperature being arrived at between bulb and water, it 
was usual to leave the thermometer at the depth where it was wanted to register for at 
least three minutes before causing it to reverse. In the case of the first sounding at any 
station when the thermometers had remained for some time exposed to atmospheric 
temperature, an immersion of five minutes was the minimum. 



CLYDE SEA AREA. 5 

The glass-encased thermometer is fixed by means of thick indiarubber rings and 
washers in a perforated brass case, and some observers have found that these rings tended 
to make the instrument somewhat sluggish in its action. I only observed this effect on 
two occasions when the rings had got displaced, and, blocking the perforations, checked the 
flow of water between the brass tube and the bulb. On altering the position of the rings 
there was no further trouble. 

There is no question as to the perfect suitability of the Negretti and Zambra ther- 
mometer for all marine work where the exact temperature at a given position is required. 
There is, however, considerable difference of opinion as to the best mechanism for insur- 
ing inversion of the thermometer at the wished-for point. I have never used the original 
wooden float with shot counterpoise, nor do I think that satisfactory results ever attended 
its employment. Magnaghi's frame was a marked improvement. In it the thermometer 
mounted on trunnions is held upright in the frame by a pin, which is raised by the action 
of the rush of water past a screw propeller, on the instrument being drawn up. At first 
there were two blades on the propeller, but the addition of a third gave it much greater 
certainty in working. When the thermometer falls over, it is clamped by a side spring, 
and retained in its inverted position until reset. A light indiarubber band passed round 
the upper part of the frame insures that the reversal takes place immediately on the pin 
being withdrawn. The Magnaghi frame in its original form, and with the addition of 
many modifications, has been largely used for deep-sea work, and has given considerable 
satisfaction. The work of the Scottish Marine Station in shallow water and amongst rapid 
currents soon revealed a number of defects. When the screw was arranged so as to reverse 
the thermometer when hauled up through less than one fathom, it was often set off by the 
pitching of the ship or by the force of the current ; and when adjusted for a longer haul, 
the exact depth at which the instrument turned over could not be ascertained, and it was 
impossible to get bottom temperatures. The method of attachment to the sounding-line 
by lashings was also found to be troublesome and slow, especially in cold and wet weather. 
The Scottish frame was accordingly devised. It is a modification of Magnaghi's, the 
screw pin with its revolving gear being replaced by a simple pin actuated by a lever, 
which is depressed by a weight or " messenger " slipped down the line, striking on the 
forked outer branch. A vice-clamp serves to fix the frame to the sounding-line at any 
point, and with great rapidity. The final form of frame was not arrived at until after 
many experiments, but thousands of observations have shown it to be convenient and 
trustworthy. The form which was found most convenient is figured in Plate L, and 
a sufficient description is attached to show the object of the various parts. An improved 
form of clamp to secure the instrument when reversed has been introduced by Messrs 
Negretti and Zambra, and is smoother in action than that shown in the figure. 

Rung's extremely ingenious messengers, made in two pieces, which can be fitted 
together on any part of the line, are used for the Scottish frame. 

The importance of having thermometers -which can be made to register at an}^ given 
depth is very great. For instance, the temperature of the surface at Clapochlar, Loch 



6 DR HUGH ROBERT MILL ON THE 

Si rival), was 42°0 on one occasion in February 1887, at 5 fathoms 42 0, 1, at 10 fathoms 
44° - 4, at 15 fathoms 45 o- 0, and at the bottom (35 fathoms) 44 0, 1. Closer observations 
showed that at 8 and 9 fathoms the temperature was 42° # 1, while at 9^ fathoms it was 
44 0, 4, showing a rise of 2°-3 in 3 feet, and a change of only o, l in the 54 feet above. 
In shallow estuaries almost all the change of temperature between surface and bottom 
sometimes takes place in a few inches of depth. In such cases, Magnaghi's frame would 
be of no service. 

Using a small boat, as I had frequently occasion to do, it is possible for the observer 
alone — with a boatman to keep the vessel in position — to work a 120-fathom line, and 
read the thermometers quite satisfactorily. It is convenient in such a case to use only 
two thermometers. The first is set and placed a few feet above the lead, which may be 
very light in still water, but must be heavy if there is a current, then lowered over the 
side, and the second thermometer attached 5 or 10 fathoms or feet, as the case may be, 
above the first. The second thermometer is set, and a messenger, previously clasped on 
the line, hung to it by a wire or cord, the whole being then lowered to the proper depth. 
The line is secured, and the interval of exposure may be taken advantage of for observ- 
ing the air-temperature, at first with the dry-bulb sling-thermometer, if rain is not falling, 
then with the wet. Three minutes having elapsed, a messenger is clasped on the line 
and let go ; the impact is distinctly felt in a few seconds, and that of the second 
messenger, released by the stroke of the first, is felt a little later. The line may then be 
hauled up, the thermometers placed upright in the boat without being detached from 
the line, then read carefully, set, and lowered again to different depths. 

On the " Medusa," on which most of the observations on the Clyde Sea Area were made, 
the arrangements for taking soundings were convenient to the verge of luxury. A hemp 
sounding-line, marked with coloured worsted at every five fathoms (and at every fathom 
for the first ten), was coiled on a drum and passed through leading blocks to a tail block 
on a derrick, which projected slightly over the port side near the bow, at a height of 8 
feet from the deck. The ship was stopped, and one man stationed at the wheel, with the 
engine reversing-gear within reach, kept her head to the sea with the line as nearty 
perpendicular as possible on the windward side, so that the vessel could not drift over 
the line. A slip water-bottle was fixed on the line, just above the lead ; two feet above 
that — so as to be one fathom off the bottom — a thermometer was clamped on and a 
messenger hung to it, in order to ultimately close the water-bottle. The whole was then 
lowered ten fathoms, another thermometer and messenger attached, the process repeated 
once, or twice if four thermometers were available, and the line was lowered until the lead 
touched the bottom. In calm weather it was allowed to remain thus ; but when there 
was any sea on, the depth was recorded, and the line raised one or two fathoms, to pre- 
vent bumping. A messenger was let go after three minutes ; and as soon as the impact 
of the last messenger on the water-bottle was felt, the steam winch rapidly hove up the 
line. As each thermometer appeared it was removed, the winch being stopped a moment 
for this purpose ; the reading could always be made and recorded by the time the next 



CLYDE SEA A.REA. 



instrument came to the surface. When the water-bottle was emptied, the thermometers 
were replaced in the same order as before, sent down to a different depth, and the process 
repeated again and again, until an observation had been made at every ten fathoms from 
surface to bottom. Then the figures, recorded by an assistant in the observation-book, 
were examined, and if there was any sudden difference between two, or any unusually 
close agreement, readings were made at intermediate depths, and this process of subdividing 
spaces was carried on until the exact form of the temperature curve had been ascertained. 
With a crew of three men it was possible, in quarter of an hour, to make and record six 
observations ; that is to say, two dips of the sounding-line with three thermometers, and 
also to observe the air temperature, barometer, wind, weather, &c. This may be contrasted 
with the time required to get the same number of observations with spirit thermometers. 
The rate of descent of the brass messengers was measured several times. Ther- 
mometers were fixed on the line at intervals of ten fathoms, and when they had acquired 
the temperature of the water a messenger was dropped. The time when it struck the 
surface of the water was noted by the seconds hand of a watch, and an assistant with 
his hand on the line said " one," " two," or " three," as the respective shocks caused by the 
impact of successive messengers, which were released by the reversing thermometers, were 
felt. The instant of hearing these words was also entered. This method was only roughly 
accurate. The time -intervals between successive shocks included not only the duration 
of falling of the weight, but the time which each thermometer when struck required 
to turn through rather more than a right angle (probably about 120°), before the loop 
holding the messenger slipped, and also the time during which the vibration passed 
up the line. These intervals were, however, practically constant in the slight depths in 
which observations were made. The following table (Table I.) summarises the experi- 
ments made in this way, and shows the rate of fall of the messenger in sea-water 
(average density, 1"0250), the figures being reduced in the last column to feet per 
second, the space marked as " ten fathoms " on the sounding-line having, at the time the 
observations were made, become equal to 62 feet, in consequence of stretching. 

Table I. — Mean Velocity of Fall of Brass Weights in Sea Water. 



Length of Run. 
Fathoms. 


Average Length 
of Run. 
Fathoms. 


Number 

of 

Cases. 


Seconds 

in Falling 

10 Fathoms. 


Average Velocity. 
Feet per second. 


2 to 5 
6 to 9 
10 

13 to 16 
21 to 34 
38 to 64 


3 

7 
10 
14 
27 
50 


15 
4 

42 
4 
5 
5 


8-7 

8-0 

7-16 

6-9 

6-4 

6-2 


7-1 
7-8 
8-6 
9-0 
9-7 
10-0 



This shows that the resistance of the water rapidly causes the acceleration of a falling 
weight to approach a limiting value ; and from the form of the curve, which expresses the 



8 



DR HUGH ROBERT MILL ON THE 



above figures, it appears that the limiting velocity does not much exceed 10 feet per 
second for any depth, supposing the line to hang perpendicularly. In cases when the 
roughness of the sea prevented the impact of the messengers from being heard or felt, it 
was accordingly customary to allow one minute as sufficient for the descent of the 
messengers — the depth, practically, never exceeding 100 fathoms. 

As bearing on the loss of time due to the travelling of vibrations up the line, the 
forty-two observations of the rate of fall for 10 fathoms were classified as in Table II., 
which shows that the limiting value was reached almost immediately. 



Table II. — Time occupied by Brass Weight in Falling Ten Fathoms through Water. 



Distance of Fall. 
Fathoms. 


Approximate 

Depth of the Run 

of 10 Fathoms. 

Fathoms. 


Number 

of 
Cases. 


Apparent Time 

occupied in Falling. 

Seconds per 10 

Fathoms. 


Mean. 


10 


to 15 
15 to 30 
30 to 60 
Over 60 


13 

13 

13 

3 


7-1 
7-2 
7-1 
74 


7-16 

J 



The impact of the messenger, after even a long run in water, was not sufficient to 
damage the thermometer ; but when a reversing thermometer was used for a surface 
observation, the shock of a messenger dropped 10 feet or more from the deck would be 
dangerous. Accordingly the thermometer at the surface was usually reversed by 
depressing the lever with a boat-hook, or by lowering a messenger along the sounding- 
line by a piece of twine. 

Much of the credit for the rapid working which was possible on the " Medusa " is due 
to the skill and alacrity of her crew, and in particular to the constant attention of her 
skipper, Mr A. Turbyne, whose unfailing good-humour made the work as pleasant as it 
was expeditious. 

Treatment of Temperature Results. — The thermometer readings were entered in the 
observation -book exactly as taken, the correction for index-error being afterwards applied 
in a column left for that purpose. The observation-book had one page devoted to each 
sounding, printed headings for position, date, hour, state of weather, &c, and a line for 
the temperature at each fathom down to 10, then for each 2 fathoms to 20, and for each 
5 fathoms to 110. The figures when corrected were published as already stated. From 
the corrected figures curves showing the vertical distribution of temperature at each 
station for each trip were drawn, the abscissae being temperature, 5 millimetres represent- 
ing one degree Fahrenheit, and the ordinates being depth, 1 millimetre representing 
1 fathom. All the vertical temperature curves in the plates illustrating this paper are 
reproduced on this scale, the paper being divided for the sake of clearness into squares 
of 5 millimetres instead of 1 millimetre. The curves thus drawn fell into a certain 



CLYDE SEA AREA. 9 

number of clearly-marked groups, which will be fully described in the sequel. In 
drawing, the various points are connected by straight lines, not by a freehand curve. 
The necessity of avoiding any theorising as to the form of the curve between fixed points 
was demonstrated by repeated observations of extraordinarily rapid changes, and even 
inversions of temperature gradient, producing sharp inflexions in the curve representing 
them. In some of the enclosed loch basins the upper part of the temperature curve 
was often sickle-shaped, and the lower perfectly straight — a state of matters which 
demanded very close observations to clearly define. It was my custom latterly to plot 
the temperatures roughly as the observations were made, and so see before leaving 
the station where it was necessary to take closer observations, in order to lay down 
the region of rapid change of curvature as completely as possible. 

From the curves the mean temperature of the vertical column of water from surface 
to bottom was obtained by drawing a straight line cutting the curve so as to leave equal 
areas between it and the curve above and below the intersection. The centre of this 
line gave the mean temperature. The exact position of the line was found by repeated 
trials, and the areas measured by counting the millimetre squares. These determinations 
were checked in a number of cases selected at random, by taking the mean of each pair 
of contiguous observations, and so by adding these means, multiplied by the distance 
between respective pairs of readings, and dividing by the whole depth, getting the mean 
temperature as accurately as possible. The two methods gave results corresponding to 
one-tenth of a degree, the limit of accuracy of the component observations. After 
the mean temperatures of about a thousand soundings had been calculated, it was found 
that they could not be utilised in the manner originally intended, although in special 
cases they furnish interesting conclusions. The mean temperature of the layers, five 
fathoms deep, next the surface and the bottom, especially the former, yield results of 
greater importance, particularly as concerns the relation of air and water temperature. 
Seasonal curves showing the changes in mean temperature of the vertical columus, and 
thus — assuming constant salinity and specific heat — the changes in total heat at the 
station, were prepared from these data. 

When dealing with enclosed lochs, and sometimes with the more open basins, it was 
convenient to draw isotherms, showing the distribution of temperature on a section of 
the region. The degree of exaggeration necessary in order to give the diagram sufficient 
breadth relative to its length varied in the different cases ; but in all it was made 
sufficient to allow of isotherms for each degree Fahrenheit being clearly laid down. The 
depth at which the temperature at each whole degree occurred was obtained from the 
vertical curves. The chief difficulty in the case of a long section was the fact that there 
was often a considerable interval of time between the various soundings. As the 
distribution of temperature was in many cases profoundly altered by a single day of 
strong wind, this fact occasionally led to great irregularities in the run of the isotherms. 
On the whole, however, the sections give a fair idea of the total amount and general 
distribution of heat in the water. In order to allow the distribution of temperature 

VOL. XXXVIII. PART I. (n t 0. 1). B 



10 DR HUGH ROBERT MILL ON THE 

to appeal directly to the eye, the sections were coloured in accordance with the principle 
that the merging of one temperature into another should be represented by the 
corresponding merging of shades or colours. The coldest water was represented in 
purple, and at intervals of 2° dark-blue, light-blue, blue-green, green, yellow-green, 
yellow, orange, and deepening shades of red were employed, so that the increasing 
warmth of the colour corresponded in the order of the spectrum with the increasing 
warmth of the water. All the sections were drawn on paper ruled in millimetre 
squares, and by counting the number of squares between successive pairs of isotherms 
the mean temperature of the whole section was readily calculated. 

In the case of a loch, however, the really interesting datum to secure is the mean 
temperature at a given time of the whole mass of water, and this was arrived at by 
the following method: — The mean temperature of each zone of 10 or 15 fathoms was 
ascertained by the process of counting squares" between the isotherms crossing the zone, 
and the figure so secured was multiplied by a factor which took account of the mass 
of water in that zone. Thus the 10 fathoms of water next the surface spreads over a 
much greater mean superficial area than the next horizontal slice of 10 fathoms, and 
the lowest zone of ten fathoms has a very small mean area indeed. Thus, if fig. 1 
(Plate XXII.) be an average transverse section of a loch, the mean temperatures of 
successive zones of 10 fathoms of which have been ascertained in the longitudinal 
section, and the lines a, b, c, &c, being the length of the side of the rectangle, having 
the same area as the section cut off between successive depths of 10 fathoms, the 
mean temperature M of the whole loch would be represented by 

-««- _ m x a + m 2 6+m 3 c-|-m^+. . . 
a+b + c+d + . . . 

where m v m 2 , &c, are the successive mean temperatues of the longitudinal zones of 10 
fathoms. This assumes that the isothermal surfaces are horizontal, which is not strictly 
true. From the few cases of observations which allowed of the construction of transverse 
sections showing isotherms, it appears that the isothermal surfaces are normally slightly 
arched in the centre, and when disturbed by transverse winds they are tilted up on one 
side nearly to the same degree as they are tilted down on the other, thus leaving the 
mean thermal condition identical with that expressed by isothermal surfaces drawn 
horizontally through the central soundings. In calculating thermal changes, all data 
are referred to half tide, as it was found impossible, from the observations available, to 
distinguish tidal disturbances from the other periodic phenomena. In the case of the 
Channel and Great Plateau, which may be looked on as bodies of water of practically 
uniform thickness throughout, the average temperature of the mass is given sufficiently 
closely by the average of the mean temperatures of the various vertical curves. 

Another very instructive method of discussion of vertical distribution of temperature 
is to construct diagrams showing thermal change in depth and time at some particular 
station. Time is marked as abscissae, depth as ordinates, and the isotherms of each 



CLYDE SEA AREA. 11 

degree, or occasionally each half degree, are inserted ; the spaces between being coloured 
as in the vertical sections. By this means the depth to which any particular tempera- 
ture penetrates, and the date at which it reaches that depth, are shown at a glance. 
The completeness of such a diagram obviously depends on the frequency with which 
observations were made, and the coincidence of the periods of maximum and minimum 
penetration with a date of observation. Characteristic deep-water stations were selected 
for this treatment, including the Channel, Skate Island, and Garroch Head in the Arran 
Basin, Gantock and Dog Rock in the Dunoon Basin, Stuckbeg in Loch Goil, Strachur in 
Loch Fyne, and Shandon in the Gareloch. 

The rate of seasonal descent of the maximum temperature was worked out from these 
sections and exhibited in the form of a curve. Special functions of temperature-change 
were selected for graphic treatment in certain cases, and these will be described in their 
proper place. 

The regional distribution of temperature was worked out for each cruise by the 
use of charts, on which the temperature at the surface, at 5, 15, 30, and 50 fathoms, as 
ascertained from the vertical curves, were laid down. These charts, however, it has not 
been considered necessary to publish, two specimens only being given. 

Terminology Employed. — In order to refer concisely to the different temperature 
conditions indicated by curves and sections, it is necessary to define certain expressions 
which I venture to use with special meanings. A mass of water at uniform 
temperature throughout is termed homothermic, and the curve of vertical temperature 
corresponding to this condition (a straight vertical line) is called a homothermic curve. 
Similarly, a mass of water, the temperature of which varies from point to point, 
is said to be heterothermic, and the corresponding curve expressing vertical distribution 
of temperature at any point is called a heterothermic curve. The heterothermicity 
of a mass of water from surface to bottom (this direction is the only one here 
considered) may be of several kinds, each typical arrangement giving a curve of 
special character. Thus, when the temperature is highest on the surface and lowest 
at the bottom, the prevailing character in summer, the resulting curve is said to have 
positive slope ; when the temperature is lowest at the surface and highest at the bottom, 
the curve is said to have negative slope. The slope of a curve is arbitrarily measured 
by the difference between the mean temperature of the superficial layer of five fathoms 
and that of the bottom layer of five fathoms. It is thus practically the same as 
vertical range of temperature between these 5 -fathom layers. When the curve 
is of one curvature throughout, it may be (l) straight when the rate of change 
is uniform all the way from surface to bottom ; (2) 'paraboloid when the rate of 
change is greatest in the superficial layers, and diminishes downward ; and (3) inverted 
when the rate of change of temperature becomes greater as the depth increases. 
These typical curves frequently occur in combination : thus a large mass of water 
may be homothermic, while an upper or lower layer may exhibit any one of the varieties 
of heterothermicity. Of these mixed types, two at least may be mentioned — the 



12 



DR HUGH ROBERT MILL ON THE 



positive or negative S-shaped curve, and the positive or negative sickle-shaped curve. 
The contorted curve, as the extreme case of heterothermicity representing superimposed 
layers of water at different temperatures, may also be mentioned. Examples of these are 
given in fig. 3 (Plate XXII.). 

Air Temperature. — For the distribution of air- temperature I depend on the data 
supplied by Dr Buchan, which are published in Part I. The air-temperature observa- 
tions, made by a sling thermometer at the time of each temperature-sounding, are of 
course affected by the diurnal range to an enormously greater degree than is the 
water-temperature. It is therefore impossible to apply them in any general way. 
Table III. gives an approximation to the mean air-temperature of the Clyde Sea Area 
for the three years under observation, by combining observations from selected stations ; 
and the results are shown graphically compared with the long period mean (1866-1885), 
by the curve, fig. 2, Plate XXII. In this and other curves of seasonal variation the 
mean value for the month is placed on the line indicating the central day of that 
month. 



Table III. — Mean Temperature of Air over Clyde Sea Area. 

1886. 



Station. 


Jan. 


Feb. 


Mar. 


A.pril. 


May. 


June. 


July. 


Aug. 


Sept. 


Oct. 


Nov. 


Dec. 


Year. 


Glasgow, . 


34-6 


34-8 


38-6 


44-4 


48-8 


54-2 


57-6 


57-0 


52-8 


50-4 


44-4 


34-0 


46-0 


Helensburgh, 


36-8 


36-5 


38-2 


44-0 


48-2 


54-4 


57-8 


56-8 


52-7 


51-1 


45-4 


36-3 


46-5 


Dumbarton, 


35-2 


34-8 


37-6 


44-4 


48-0 


54-3 


57-8 


56-3 


53-2 


50-3 


43-2 


33-8 


45-7 


Greenock, . 


354 


34-8 


37-4 


43-2 


47-2 


53-4 


56-8 


56-7 


53-0 


50-3 


44-2 


35-0 


45-6 


Rothesay, . 


36-0 


36-6 


39-0 


45-0 


47-8 


53-9 


56-6 


56-2 


53-5 


51-1 


45-0 


36-0 


46-4 


Lamlash, . 


39-4 


37-1 


38-0 


44-0 


47-6 


53-2 


56-1 


55-9 


53-8 


51-0 


46-5 


38-6 


46-8 


Pladda, 

Mean, 


37 


38-3 


38-0 


44-1 


47-4 


52-1 


55-7 


55-6 


53-6 


51-7 


46-3 


38-0 


46-5 


36-3 


36-1 


38-1 


44-2 


47-9 


53-6 


56-9 


56-4 


53-2 


50-8 


45-0 


36-0 


46-2 




1887. 


• 






Glasgow, . 


38-9 


4C0 


39-4 


43-5 


51-1 


58-9 


60-1 


57-4 


52-6 


45-1 


40-4 


37-3 


47' 1 


Helensburgh, 


37-5 


39-3 


37-8 


41-7 


48-4 


S 8-o 


6o - o 


57"° 


52-0 


43-6 


39-4 


35-8 


45'9 


Dumbarton, 


38-1 


40-0 


38-8 


43-1 


50-1 


58-4 


60-3 


57-1 


52-2 


45-3 


41-5 


37-0 


46-8 


Greenock, . 


38-8 


40-0 


38-7 


43-0 


49-7 


58-8 


61-0 


57-1 


52-4 


45-5 


40-8 


37-3 


46-9 


Rothesay, . 


39-0 


41-7 


40'o 


43-8 


50-6 


58-4 


59-4 


57-1 


53-2 


46-1 


41-8 


37-6 


47 '4 


Lamlash, . 


40-6 


41-7 


40-1 


42-9 


49-6 


58-7 


58-7 


57-2 


52-4 


46-2 


43-1 


393 


47-5 


Pladda, . 
Mean, 


40-5 


41-6 


40-7 


43-2 


49-9 


58-8 


58-9 


57-4 


53-1 


46-3 


42-2 


38-8 


47-6 


39-1 


4o - 6 


39'4 


430 


49-9 


5 8-6 


59'8 


S7'2 


52-6 


45-4 


41-3 


37-6 


47 -o 



Note. — Figures in this type — 473 — are approximate only. 



CLYDE SEA AREA. 



13 



Table III. — continued. 



1888. 



Station. 


Jan. 


Feb. 

37-0 


Mar. 


April. 


May. 


June. 
54-1 


July. 


Aug. 


Sept. 


Oct. 


Nov. 


Dec. 


Year. 
46-7 


Glasgow, . 


39-8 


37-1 


43-2 


50-3 


55 6 


56-2 


52-8 


48-4 


44-2 


42-2 


Helensburgh, 




38-6 


38-3 


38-2 


44-4 


50-3 


54-9 


55-4 


56-5 


53-9 


49-2 


45-1 


426 


47-3 


Dumbarton, 




39-8 


36-3 


36-3 


43-0 


49-5 


54-0 


55-3 


56-3 


52-7 


47-5 


44-4 


41-0 


46-3 


Greenock, 




39-7 


36-2 


36-5 


42-9 


49-5 


53-5 


54-5 


56-4 


53-0 


47-8 


44-4 


41-8 


46-3 


Rothesay, . 




409 


37-7 


37-7 


43-8 


49-8 


54-5 


55-1 


55-8 


53-1 


48-2 


44-2 


42-3 


46-9 


Lamlash, . 




41-2 


38-1 


37-6 


42-4 


49-1 


52-8 


54-2 


55-0 


52-2 


48-0 


44-2 


44-0 


46-6 


Pladda, 




42-2 


37-9 


37'5 


42 - 5 


49'° 


53"° 


54-6 


55-6 


52-4 


48-1 


43-6 


43-8 


467 


Mean, 


40-3 


37-4 


373 


43" 2 


49-6 


53-8 


55'° 


56-0 


529 


48 '2 


44-2 


42-5 


467 




Period 1866-85. 






Mean, 


39-4 


39-9 


40-6 


45-0 


49-5 


55-1 


57-7 


57-8 


53-8 


47-6 


42-1 


39-4 


47-3 



Note. — Figures in this type — 47*3 — are approximate only. 



Temperature Trips. 

The general arrangements and routine of the trips in the Clyde Sea Area made in the 
" Medusa" have already been explained in Part II. p. 674 et seq., and the temperature 
observations which form the basis of this part of the discussion were made simultaneously 
with the collection of samples of water for the determination of salinity. 

Temperature observations were the more comprehensive in two ways. They were 
made at a few additional stations, and they were continued at somewhat irregular 
intervals for more than a year after the salinity observations had been stopped. With 
the exception of the trips for August 1886 and August 1887, all the thermometer 
readings up to September 1887 were made by myself personally. After that date they 
were made by Dr Murray or his assistants. The serial observations off Garroch Head 
intermediate between the regular trips were made by Mr Ttjrbyne. 

The following list gives the number of separate temperature soundings made at each 
station, the date of the first and last observation, and, where the data have not been 
already given in Part II., the position at which observations were made. In addition, 
surface-temperature was frequently observed at special points, particulars of which will 
be given in their proper place. The occasional observations made before 1886 are not 
taken into account here. 



14 



DR HUGH ROBERT MILL ON THE 
Table IV. — Stations where Observations of Temperature were made. 











Date of Observations. 


Division and Station. 


Depth. 

Fathoms. 


Position. 


No. of 
Obs. 


















First. 


Last. 


Gakeloch — 












Garelochhead, 


10 


See Pt. II. p. 674. 


20 


13.4.86 


6.9.88 


Shandon, 






21 


J) 


23 


j) 


25.10.88 


Row II., . 






23 


JJ 


15 


)> 


6.9.88 


Row I., 






12 


JJ 


14 


!) 


)! 


Various, 






... 




9 






Loch Goil — 












Lochgoilhead, 


27 


See Pt. II. p. 674. 


16 


17.6.86 


3.9.88 


Stuckbeg, .... 


40 


?» 


21 


13.4.86 


23.10.88 


Carrick Castle, 


20 


Carrick Castle, W. \ mile. 


2 


25.3.87 


29.9.87 


Mouth, .... 


8 


Carrick Castle, N.W. \ N. f- mile. 


9 


5.8.86 


10.2.88 


Loch Long — 












Arrochar, .... 


10 


See Pt. II. p. 674. 


23 


13.4.86 


3.9.88 


Tkornbank, .... 


35 


?) 


16 


17.6.86 


23.10.88 


Knap, ..... 


25 


Mid-channel off Knap Point. 


2 


5.8.86 


21.9.88 


Holy Loch — 












Head, 


5 


Kilmun Pier, E. by S. \ mile. 


8 


14.4.86 


8.8.87 


Kilmun, .... 


10 


See Pt. II. p. 674. 


8 


12.2.87 


8.9.88 


Mouth 


15 


Strone Point, E. by N. \ K \ mile. 


6 


16.6.86 


10.2.88 


LochStrivanandButePlateau — 












Loch Strivan Head, 


12 


See Pt. II. p. 675. 


20 


14.4.86 


20.10.88 


Clapochlar, . 




40 


JJ 


24 


JJ 


JJ 


Mouth, 






34 


Strone Point, E.NE. \ mile. 


12 


18.6.86 


20.9.88 


Various, 










11 






Rothesay Bay, 






12 


Rothesay Pier, S.W. \ mile. 


3 


15.4.86 


27.12.86 


Bogany, 






27 


See Pt. II. p. 675. 


19 


14.4.86 


8.9.88 


Kyles of Bute — 












Strone Cotes, 


20 


jj 


17 


21.4.86 


20.9.88 


Burnt Islands (" Angle "), . 


28 


J) 


18 


20.4.86 


>> 


Ormidale (Loch Ridun), 


10 


JJ 


16 


JJ 


>> 


Loch Fyne — 












Cuill, . 


15 


JJ 


21 


20.4.86 


17.10.88 


Dunderawe, . 






35 


JJ 


23 


JJ 


JJ 


Inveraray, . 






60 


JJ 


31 


19.4.86 


3.9.89 


Strachur, 






75 


)J 


27 


20.4.86 


18.10.88 


Furnace, 






35 


JJ 


20 


19.4.86 


16.10.88 


Paddy Rock, 






18 


Paddv Rock, E.S.E. 2 cables. 


8 


29.3.87 


>) 


Minard, 






10 


Minard Castle, S.W. by W. \ mile. 


3 


5.2.87 


10.5.87 


Gortans, 






30 


See Pt. II. p. 675. 


21 


19.4.86 


16.10.88 


Otter II., 






20 


>) 


11 


10.8.86 


16.10.88 


Dunoon Basin — • 












Dog Rock, . 


50 


jj 


19 


13.4.86 


3.9.88 


Coulport, 






42 


>> 


18 


14.4.86 


JJ 


Blairmore, . 






35 


Blairmore, W., 8 cables. 


9 


24.9.86 


24.10.88 


Strone Point, 






30 


See Pt. II. p. 675. 


15 


13.4.86 


8.9.88 


Gantock, 






55 


JJ 


22 


14.4.86 


JJ 


Cloch, . 






46 


Cloch Light, S.E. by E. \ E. \ mile. 


3" 


5.8.86 


22.9.88 


Wemyss, 






43 


Wemyss Pt., S.E. by E. \ E. \ mile. 


2 


6.8.86 


23.9.86 


Knock, 






40 


See Pt. II. p. 675. 


13 


jj 


25.10.88 


Various, 






... 




2 







CLYDE SEA AREA. 



15 



Table IV. — continued. 











Date of Observations. 


Division and Station. 


Depth. 


Position. 


No. of 








Fathoms. 




Obs. 


First. 


Last. 


Abran Basin — Central — 












Otter I., 


30 


See Pt. II. p. 675. 


13 


19.4.86 


28.9.87 


Kilfinau, .... 


85 


Otter House, E.S.E. 2\ miles. 


12 


29.3.87 


19.10.88 


Skate Island, 


107 


See Pt. II. p. 675. 


32 


27.3.86 


19.10.88 


Ardlamoiit, .... 


30 


)> 


16 


20.4.86 


20.9.88 


Inchrnaruoch, 


88 


>) 


12 


9.6.86 


15.2.88 


Arran Basin — Eastern — 












Garroch Head, 


60 


VI 


40 


17.4.86 


29.10.88 


Brodick, .... 


90 


>J 


20 


15.4.86 


19.8.88 


Lamlash, .... 


14 


Lamlash Pier, N.W. 6 cables. 


5 


17.4.86 


31.3.87 


Largybeg (and near it), 


60 


See Pt. II. p. 675. 


10 


12.8.86 


10.12.87 


Various, .... 




... 


2 


... 




Arran Basin — Western — 












Off Loch Rauza, . 


70 


L. Ranza Castle, S. by E. \ E. H mis. 


10 


9.2.87 


5.2.88 


Carradale, .... 


80 


See Pt. II. p. 675. 


22 


19.6.86 


22.3.88 


Ross Island, 


45 


Ross Island, W. If miles. 


3 


9.12.87 


20.3.88 


Davaar, .... 


30 


Davaar Light, W. If miles. 


3 


18.6.87 


22.9.87 


Various, .... 


... 


... 


5 




... 


Great Plateau — 












North-west, 


22 


See Pt. II. p. 675. 


43 


16.4.86 


20.1.88 


Southern, .... 


27 


it 


21 


)> 


20.1.88 


Campbeltown Loch, 


8 


Off shipyard, mid-channel. 


6 


18.4.86 


8.3.88 


Channel — 












Sanda, 


40 to 60 


See Pt. II. p. 675. 


8 


16.4.86 


21.3.88 


Deas Point, ... 


50 


Deas Point, N. 1| mile. 


3 


19.6.86 


17.3.88 


Cantyre, 


60 


Mull of Cantyre Light, N. by E. 
2£ miles. 


5 


16.4.86 


31.3.88 


Various, .... 


... 




2 


... 





The work to be reviewed comprises 900 temperature soundings, or not less than 6000 
separate thermometer readings, taken at about 75 stations during a little more than three 
years. In that time 23 separate temperature trips were made, in each of which the 
whole Area was gone over with some approach to completeness, and there were several 
occasional observations between these trips. Vertical temperature sections for sixteen 
of these trips from the Channel to Cuill are given in Plates VIII. to XL 

Trip I., April 1886 (See Part II. pp. 677-678).— The early months of 1886 
were characterised by low air-temperatures over the whole Area, the temperature 
for January, February, and March averaging more than 2° below the normal 
for that time of year. A preliminary observation at Skate Island on March 
27 gave an average mean temperature of 41° "3 for the vertical section; and as on 
April 19 the mean was 41°*6, it would appear that the minimum mean temperature 
occurred in March, and that there had been very little heating during the earlier 



16 DR HUGH ROBERT MILL ON THE 

part of April. On this trip, indeed, the temperature at every part of the Area was lower 
than on any subsequent occasion in the whole period during which observations were 
carried on. Observations were made from the 13th to the 21st, omitting the 18th, and 
the prevailing character of the whole region from the Channel to the loch-heads was 
uniformity. The surface temperature indeed varied a few degrees, averaging about 44° *5 
for all parts except the Channel and Loch Fyne (from Otter to Strachur), where it was 
about 42° '5. The surface water formed a thin layer: at 15 fathoms the average 
temperature was about 41° "5 for all parts except the Channel and Loch Fyne, where it 
was about 42°, and this distribution held good to the bottom. Between 10 or 15 
fathoms and the bottom there was not in any part a greater variation than o, 2. The 
mass of the water in the Gareloch and Loch Long had the temperature 41°'8, which 
may be taken as typical of the lochs and basins. Loch Fyne, however, had the mean 
temperature of 42° *0, and so also had the Channel. This difference of temperature, 
although small, is significant. It shows that the Area, as a whole, had cooled down more 
than the open water of the Channel, influenced by the Gulf Stream, and more 
than the doubly enclosed water of Loch Fyne, which had not lost the whole of its 
previous summer's increment of heat. 

The prevailing winds for some time previously had been northerly and north- 
easterly : the conditions during the trip were anticyclonic. The result was in almost 
every case a down-loch wind, which was strongly felt in Loch Fyne and Loch Strivan. 
The observations of density showed evidence of upwelling at the head of all the lochs, 
and this was confirmed by the temperature sections for Loch Fyne and Gareloch, in 
both of which the isotherms had a definite seaward dip, showing upwelling of cooler 
water from below. 

The mean temperature of each sounding, the surface-temperature, and the tempera- 
ture at 30 fathoms are shown on map 1 in Plate XXI. as a type of temperature 
distribution at the spring minimum. 

During the trip there was a comparatively rapid heating of the water in progress, 
observations on the Gareloch on the 13th and 21st showing a gain of from 2° to 3°. 

The seaward reaches of the Firth of Forth were practically at the same temperature, 
averaging 41 0- 5, as ascertained by a trip from Granton to the Isle of May on April 23rd. 

Trip II, June 1886. — The central day of this trip was sixty-one days after the 
central day of Trip I. In the interval the curve of air-temperature was parallel to the 
long period mean, but at least l°-5 lower. The winds had been prevailingly northerly. 
During the trip (June 16-22) the wind changed to north-west and west, and at times 
blew strongly. There was bright sunshine most of the time, contrasting with the 
weather of the previous six weeks, when there was a marked lack of sunshine. 

In Loch Goil and Loch Strivan there were strong down-loch winds during 
observations; in Loch Fyne the wind was blowing freshly up the loch, and in 
Loch Long and the Gareloch the wind was transverse, from the west. Eapid heating 
had taken place everywhere on the surface, especially in the seaward division ; the 



CLYDE SEA AREA. 17 

surface temperature was over 50° everywhere south of Bute, but nowhere reached that 
figure to the north of it. In the Channel, indeed, the surface temperature was somewhat 
lower, although that at the bottom was higher, than inside the Great Plateau. 
The general condition may be expressed by saying that the water was growing rapidly 
warmer from the surface downward and from the ocean inward. Warming from the 
ocean was evidently in progress, by the tide drawing inward over the great counter 
of the Plateau slices of water from the mass, at uniform temperature of over 47°, 
outside ; this was chilling the surface layers, but, in virtue of its superior salinity, 
warming the lower layers. That this was the case was shown by the rapid seaward 
slope of the isotherms in vertical sections of both branches of the Arran Basin. 
The warming had proceeded to the greatest depth just inside the Great Plateau, 
where 46° was found at 30 fathoms, and its influence gradually diminished landward, 
until at Otter the isotherm of 40° reached the surface, and at Gantock rose to 
6 fathoms. Solar surface-heating was most marked in the East Arran Basin. The 
influence of configuration was very beautifully brought out in the deep basins of 
Loch Goil and Loch Fyne. The bottom at Stuckbeg had the temperature 41°*9, 
a rise of only half a degree since April, while in Loch Fj^ne the very remarkable 
phenomenon of a mass of cold water sandwiched between warmer layers was 
observed. 

The mass of water at uniform temperature, which made the lower part of all the 
curves of vertical temperature in April perpendicular lines, was no longer found. There 
was everywhere (Upper Loch Fyne excepted) a positive slope in the curve, showing 
continuous, though not uniform, warming from the surface downward. In this trip 
the salinity observations showed, much better than the temperature, the effect of wind 
in setting up vertical circulation. 

Trip IIL, August 1886. — The observations (by Mr J. T. Morrison) were made in 
two parts, the first from August 3rd to 7th inclusive, the second from the 10th to 
the 13th. The interval between this trip and that of June was fifty days. The 
weather of this period showed air-temperatures rather less than a degree below the 
average for the season ; the first and last w T eek of July were hot, but the middle 
fortnight colder, and the early part of August nearly came up to its normal warmth. 
The prevailing wind had been south-westerly. During the trip the weather was 
broken, several small cyclones passing and producing variable light winds, usually from 
the south-west, and blowing up most of the lochs. 

The distribution of temperature was practically the same as in June, although 
the water was, throughout, warmer. In the North Channel the whole mass of oceanic 
water, remaining homothermic, had warmed up to 52° '7, and pouring over the Great 
Plateau, as in June, cooled the upper and warmed the lower layers in the Arran 
Basin. The isotherms on the sections from Channel to loch-heads dipped, as before, 
strongly seaward. As before, the water in the deeper parts of the Arran Basin had 
warmed more slowly than that outside, and remained colder, being 46° at 50 fathoms, 

VOL. XXXVIII. PART I (NO. 1). C 



18 DR HUGH ROBERT MILL ON THE 

where the Channel was 52° '5. And, as before, the deep isolated loch-basins retained 
still colder water, the minimum temperature being 43° in Loch Fyne. The minimum 
there occurred, as in June, about half way between surface and bottom, the vertical 
curves being sickle-shaped. The maximum effect of sun-heating was shown near the 
head of the lochs and in the southern branches of the Arran Basin. 

During this period the temperature in the North Sea, off the mouth of the Firth of 
Forth, was about 52° from surface to bottom, more than a degree colder than off the 
mouth of the Clyde Sea Area. 

From August 24th to 30th a short trip was taken in the Dunoon Basin and Loch 
Fyne, and a few observations were also made in the Arran Basin and Loch Fyne from 
September 13th to 17th. The data obtained fall into their natural places in discussing 
the separate stations and regions. They served to fix the period of surface maximum 
temperature for the year, but are not otherwise of general interest. 

Trip IV., September 1886. — The general climatic conditions of this trip, lasting from 
the 22d to the 27th, are given in Part II. p. 680. It occurred forty-eight days later than 
Trip III. Air-temperature was a little below the normal during August and September, 
and the w T eather was fine on the whole, although rather rainier than the average. From 
September 10th to 2 2d an anticyclone prevailed, with very light airs, and during the 
greater part of the trip there was a calm. A cyclone passing from the 25th to the 27th 
brought a fresh westerly breeze, blowing transversely to the Central Arran Basin and 
Loch Goil while these regions were being examined. This trip may be said to have 
been taken at the period of the annual maximum : the maximum for the surface water 
was past, and cooling had just commenced, but the maximum of the deeper layers was 
not yet reached. The oceanic water was still the warmest, a fact that was very clearly 
ascertained, as a larger vessel than the " Medusa " was available, and soundings were 
made well out in the North Channel, south of the Mull of Cantyre and across toward 
the Galloway coast. The Channel was filled with water at the uniform temperature of 
54°' 5, and from the Channel inward the temperature diminished. The coldest water in 
the Arran Basin was a little under 48°, and occurred at the bottom off Skate Island. 
The same temperature was reached at 15 fathoms in Loch Goil, where the bottom 
temperature sank to 44°'3, and at 25 fathoms in Loch Fyne, where the bottom was 
slightly under 44°. These deep lochs had thus kept their water more than 4° colder 
than the open basins, and more than 10° colder than the open sea. On this occasion the 
surface water was everywhere warmest, and the bottom water coldest, all indications of 
an intermediate minimum having vanished from Loch Fyne. 

It should, of course, be remembered that practically all the observing stations were 
midway between the coasts of the various natural regions examined, so that the effects of 
local heating on a shallow shore were not observed. This effect is, however, considerable, 
and in some places may materially raise the temperature of the shallow water, but the 
broad inrush with every tide of the uniformly heated water from the Channel is unques- 
tionably the most important factor in raising the temperature for the year. That its 



CLYDE SEA AREA. 19 

influence is greater than that of solar radiation is perfectly shown by the very much 
slower rate of warming in the masses of water cut off from free communication with the 
ocean, but more exposed in every way to solar power from the much greater influence 
on their waters of the heated land and warm surface drainage. 

The process of heating-up from a practically uniform coldness in all parts of the Area 
has so far brought out month by month with increasing distinctness the enormous power 
of physical configuration in dominating thermal changes, — none the less because the 
process of heating-up was probably retarded on account of the abnormal coldness of the 
whole spring and summer. The average temperature of each vertical sounding, the 
surface temperature, and the temperature at 30 fathoms are given on map 2, Plate XXL, 
as a typical example of the distribution of warmth at the autumn maximum. 

Trip V., November 1886. — This trip, fifty-two days later than that of September, 
occupied the time from November 11th to 18th, excluding the 14th. It commenced to 
take account of the cooling-down consequent on the excess of radiation from the surface 
after sunset over the radiation to the surface during day-light. The typical character of 
the observations was rather spoiled by the exceptional warmth of the air in October and 
November, the mean of each month being about three degrees above the average. This 
was particularly the case in the landward portion. The rainfall of October was much 
below the average. Easterly winds were common, with frequent storms, and the weather, 
although unusually bright, was disturbed. From November 1st to 4th there were strong- 
south-westerly and westerly winds. The early part of the cruise was favoured with fine 
weather, calm and showery, with snow on the hills. The landward portion, Loch Fyne 
excepted, was examined in these conditions. On the 14th, when no work .was done, 
there was a south-westerly gale; on the 15th the Kyles of Bute and East Arran 
Basin were worked in a stiff south-westerly breeze. The 16th and 17th were squally, 
and on these days the West Arran Basin and Loch Fyne were visited. The 18 th being 
calm, though hazy, was devoted to the Great Plateau, and on the 19th work was stopped 
by a gale from the south-west. 

Surface-cooling was in progress everywhere. The whole mass of water beyond the 
Plateau had cooled down to about 50° "5, but was still warm enough to exercise a 
distinctly warming action on the deep water of the southern end of the Arran Basin, 
although the surface of that basin had cooled to a lower temperature. Excluding the 
extreme instances of highland isolation, Lochs Goil and Fyne, the average temperature 
of the Area at the surface was 49° "5, and at the bottom 51° - 5. Thus while the whole of 
the shallow water and of the Dunoon Basin had cooled down from three to six degrees 
since September, in the Arran Basin the temperature at 25 fathoms was the same as 
during Trip IV., and below that depth there had been a marked heating. The slope of 
the curves of vertical temperature had, in fact, been inverted, and assumed the negative 
or winter form, the maximum temperature being at or near the bottom. 

In Loch Fyne and Loch Goil surface-chilling had set in strongly, but the bottom 
water remained cold (44°'5 to 45°'5), and the result was a warm intermediate layer, 



20 DR HUGH ROBERT MILL ON THE 

losing heat upward to meet the coming winter's cold, and passing on heat downward to 
neutralise the cold of the past winter, which had remained as in an ice-house all summer 
under the ill-conducting blanket of water cut off from free circulation. 

Trip VI, December 1886. — Forty-one days separated the middle of Trip V. from that 
which lasted from the 22nd to the 30th of December. The exceptional warmth of 
November had given place to an exceptionally cold December, the mean temperature of 
the air over the Area being 3° below the average. The latter part of November had been 
wet and stormy, and December also had the usual character of a West Coast winter month, 
with strong variable winds and much rain. During the trip every kind of weather was 
experienced. Loch Long, Loch Goil, and the upper part of the Dunoon Basin were 
studied on the 22nd, with a fresh northerly breeze and heavy rain ; the rest of the Dunoon 
Basin and Loch Strivan on the 23rd, with light varying airs. On the 24th in West Arran 
Basin a stiff breeze blew from the N.W., and on the 25th on the Great Plateau and Channel 
a gale sprang up from the S.W. On the 26th and 27th the Arran Basin was worked 
through in calm haze with snow-showers, on the 28th a westerly gale with heavy squalls 
drove the " Medusa " into the Gareloch, and the 29th and 30th allowed Loch Fyne to be 
examined in bright, calm weather, the hills snow-clad, and the surface of the loch in some 
places coated with ice. The distribution of the ice and its physical conditions have been 
already described (see Part II. p. 681). Under the ice, at the depth of 2 inches, the 
temperature was 35°"9, and at 6 inches 41°, showing the extreme thinness of the cold upper 
layer. 

During this trip the temperature of the air was much lower than that of the water, 
and a number of curious mirage-effects were observed, the Irish coast appearing elevated 
above the water, and steamers seeming to be pursuing their course underneath the land. 
The w r ell-known appearance of Ailsa Craig as a mushroom was also clearly seen. Cooling 
had gone on steadily from the surface throughout, but, except near the heads of lochs 
and in shallow water, the surface warmth ranged between 45° and 47°, the lower layer 
being everywhere warmer, and in the open basins the maximum occurred at the bottom. 
In Loch Fyne the bottom cold layer was thinned down, but had not disappeared, and 
Loch Goil showed the same effect in a less prominent way. In the North Channel the 
water was warmer than anywhere else, 48°*5 from surface to bottom, but the effect of 
surface- cooling made itself felt on the Great Plateau and in the whole of the rest of the 
Area. It is evident that the influence of the tide is a warming one, even in December, 
the ebb carrying out the cold surface water, and the flood carrying in warmer oceanic 
water. 

Trip VII , February 1887. — Observations were made between the 3rd and 12th, 
excluding the 6th, and the trip was forty-three days after that of December. Air- 
temperature during January had been close to the average for that month, and in 
February it was decidedly higher, although in the latter month there was a good deal of 
snow on the surrounding land. The weather in the earlier part of the cruise was under 
the influence of a cyclone producing strong winds from the west on the 1st, south on the 



CLYDE SEA AREA. 21 

2nd and 3rd, south-west on the 4th and 5th, when Loch Fyne was examined during an 
up-loch wind. On the 7th, Loch Strivan was visited during a stiff south-easterly breeze 
blowing right up the loch. The rest of the trip took place in anticyclonic conditions, 
clear skies and hard frost prevailing with low-lying mist over the water, which greatly 
impeded the work, making it impossible to attempt observations in the Channel. Thin 
ice was floating along the shore of the Dunoon Basin, from Hunter's Quay to Toward, at 
the head of Loch Long, and in particular in Loch Goil, where the observations had in 
consequence to be reduced in number. The surface water necessarily varied greatly in 
temperature on account of the rapid and frequent changes of weather, but it was always 
coldest, and below 5 fathoms the water was almost homothermic in all parts except Loch 
Fyne and Loch Long. The mass of the water in the Area had a temperature not varying 
half a degree from 44°. The distribution of warmth was unusual, since for the first time it 
appeared that the water on the Great Plateau was, throughout, colder than that in the Arran 
Basin. This apparent anomaly may be partly explained by the fact that no observations 
were obtained in the Channel, but the distribution is confirmed by the observations near 
the head of the various basins, where at all depths water somewhat warmer than that near 
the Plateau was found. This seems to indicate that the cooling by radiation of the Sea 
Area had slackened, and that the Channel water being now slightly colder than that inside, 
was rapidly lowering the temperature of the seaward division by tidal interchange. Loch 
Goil, where the maximum temperature of the Area (47°'3) now occurred at the bottom, 
and Loch Fyne, where the maximum (46° '5) had not worked its way quite so far down, 
may have helped to maintain the higher temperature at the head of the Dunoon and 
Arran Basin by outflow. In Loch Strivan the very remarkable juxtaposition of two 
homothermic masses of water at different temperature, already referred to in describing 
the methods of observing (p. 5), was found. From the surface to 9 fathoms the tem- 
perature was uniformly 42°. At 9 J fathoms it was 44°, and this temperature (rising about 
one-tenth of a degree) was maintained to the bottom in 35 fathoms. 

Trip VIII. , March-April 1887. — The trip, occurring fifty days after that of 
February, commenced on March 25th and ended on April 3rd, no observations having 
been made on March 28th or April 1st and 2nd. March had been a colder month than 
February as regards the air. It was, indeed, almost as much below the seasonal average 
as February had been above it. There had been a good deal of snow. The weather of 
the period during which observations were made was very stormy. A passing cyclone, 
on the 24th and 25th, brought strong winds, shifting from south-west to north-west, 
blowing right down Loch Goil and the Gareloch, when they were visited. The north-west 
gale blew strongly on the 27th and 28th, transversely to Loch Fyne ; but on the 29th 
and 30th, when that loch, the West Arran Basin, and Channel were worked over, it 
gave place to anticyclonic weather, calm and hazy. This fine spell was short-lived : a 
north-westerly gale commencing on the 31st kept the "Medusa" a prisoner in Lamlash 
Bay until April 3rd, when the final observations in the East Arran Basin were made. 

This trip came nearest to the minimum for the season, but the water temperature 



22 DR HUGH ROBERT MILL ON THE 

was neither so low nor so uniformly distributed as in April 1887. The surface water 
had once more commenced to warm up, especially in the seaward portion, and there was 
a slight fall of temperature toward the bottom. The mass of water in the Channel 
averaged 44° '5 ; in Loch Goil and the Upper Basin of Loch Fyne it was warmer, cooling 
having taken place very slowly. The Arran Basin had on the whole a temperature 
under 43°'5, and the Dunoon Basin and shallow lochs were slightly colder than this. 

This trip found the Channel warming up, and almost arriving at the same degree 
as the deep isolated lochs which were still passing down the heat of 1886. The open 
basins, which had cooled more rapidly, had reached their minimum, and so, having just 
begun to heat up again, were colder than either the free or the nearly completely inclosed 
areas. 

Loch Lomond and Loch Katrine, fresh water lakes, which were visited just before 
the Clyde trip, had the temperatures of 41 o, and 40° "2 respectively throughout their 
whole depth in the deepest parts. 

Trip IX., May 1887. — The observations were made forty-one days after Trip VIII. , 
and occupied from May 6th to 11th, no work, however, being done on the 8th. In 
April the air-temperature had been considerably below the average for the season, and 
snow had often fallen ; but May was, so far as regards warmth, a normal month. From 
May 1st to 8th the weather was calm, with light and irregular wind. On the 9th it 
was blowing half a gale from the west, and temperature observations were made in the 
West and Central Arran Basin, but the rough sea put a stop to the work. On the 10th 
Loch Fyne was visited with a fresh westerly breeze, blowing, on the whole, up the loch. 
On the 11th a light down-loch wind was found in Loch Strivan. 

The surface temperature was highest in Loch Fyne and Loch Goi], both of which 
had cooled down in the lower layers until they were practically of the same temperature, 
as the slightly warmed mass of the open basins outside, which below 15 fathoms of 
depth had a temperature of from 45°"0 to 44°*3, the West Arran Basin being somewhat 
warmer, probably on account of its freer communication with the open sea. In the 
Channel the temperature of the whole mass of water was 46°. Inside, the surface was 
everywhere warmer, and the water below 10 fathoms everywhere colder than this figure. 
As in other cases when a homothermic condition was beginning to be disturbed by 
surface-heating, there were several instances of intermediate maxima or minima. In 
Loch Fyne a very feeble indication of the kind of distribution which characterised June 
and August 1886 was detected, and similar anomalies were noticed on the Great Plateau, 
in the Arran Basin, and near the head of the Dunoon Basin. Evidently when there is no 
marked stratification of water due to a heterothermic condition, the disturbing effects 
of change of salinity would have freer play than at other seasons in determining vertical 
movements. 

Just before this trip Dr Murray had made an extensive series of observations on 
the northern lochs of the West Coast and the fresh water lakes of the Great Glen. In 
a depression of 137 fathoms off Scarba, in the Atlantic, the temperature from surface to 



CL^DE SEA AREA. 23 

bottom was found to be 45° '7, corresponding closely with the condition of the North 
Channel, the rise of 0°'3 in the interval between the two sets of observations being 
insignificant. Loch Linnhe, fairly open to the sea, showed a temperature of 45° *5 on 
the surface, a minimum of 44 0, 3 at 15 fathoms, and thence a rise to 44°"9 on the bottom 
in 50 fathoms. Loch Etive, the most completely inclosed sea- water basin on the coast 
of Scotland, showed in the deepest part surface water at 48°'4, a minimum of 44°*3 at 
10 fathoms, and a rise to 47° "6 on the bottom, a condition very similar to that of Loch 
Fyne at the same period of 1886. In Loch Morar, the deepest fresh- water lake in 
Scotland (175 fathoms), the surface temperature averaged 43°'5, and all below 40 fathoms 
was constant at 42°, while in Loch Ness nearly the whole mass of the water was at 
41° "5. All the observations show clearly that the more completely a deep basin is cut 
off from the sea, the more slowly is its water influenced by the advance of summer heat. 

Trip X., June 1887. — This trip, lasting from the 13th to the 18th, was thirty-eight 
days later than the preceding one. The temperature of the air during June, as a whole, 
was 3° above the average of the season for the Clyde Sea Area, while May had been 
a month of average warmth. June 1887 was indeed the warmest on record, and the 
great anticyclone which prevailed for the first half of the month is remembered by the 
accident of including the days when the Queen's Jubilee was celebrated. Almost the 
whole cruise was carried out in intensely hot, quite windless, cloudless, but slightly hazy 
weather. On the 13th, however, there was a great deal of heavy rain, and on the 14th, 
when Loch Goil, Dunoon Basin, and Loch Strivan were examined, there were frequent 
drizzling showers. 

Solar radiation had here a perfect opportunity for showing its utmost power, and the 
temperature of the surface water was naturally greatly raised. On the 16th, 17th, and 
18th, the hottest days, the surface may be said to have stored, on the average, heat 
enough to warm it by 2° per day. At no time in the summer of 1886 were such high 
surface temperatures observed. 

Even in the Channel the surface water was warmer than that beneath, although the 
range was, as it always is, less than in any other part of the Area where the depth is 
equal. The range was from 52°*5 to 48°, the average being almost 2°*5 warmer than in 
May. The Arran Basin, as a whole, had heated up about 4° throughout, and was 5° 
warmer than in June 1886. This was particularly noticeable in the Western Branch, 
where the temperature was considerably higher than in the equally deep parts of the 
Eastern Branch. During the cruise the increase of temperature seemed to be due rather 
to solar than to oceanic heating, and a prolonged series of hourly observations on the 
Great Plateau furnished some important suggestions as to the mechanism of the interchange 
of water by tidal currents. The great range between the temperature of surface and 
bottom water on this occasion made it peculiarly opportune for an experiment to 
determine the movement of the water. The deepest part of the Central Arran Basin 
was filled with water everywhere over 46°, except at the upper end (next Loch Fyne), 
where a mass of water at slightly lower temperature was found. This cold mass was 



24 DR HUGH ROBERT MILL ON THE 

in the form of a layer extending from 25 fathoms to the bottom at Kilfinan, but thinning 
away until at Inchmarnoch it was only 10 fathoms thick, and surrounded above and 
below by warmer water, evidently influenced by the ocean. A like remnant of colder 
water was found in a similar position at the head of the Dunoon Basin. The deep 
lochs were comparatively little affected by the rapid rise of air temperature. In Loch 
Fyne the minimum, not quite at the bottom, was 45°, and in Loch Goil the minimum 
at the bottom was 44°"9. The Gareloch was, as a whole, the warmest division of the 
Area, but high surface temperatures were found in all the sea-lochs, the absolute maximum 
being 60° in Loch Long. The influence of a long spell of hot dry weather on narrow 
waters is obviously not confined to the incidence of solar radiation on the surface. The 
water flowing in from the land is heated up by trickling in shallow streams across the 
hot rock or sand, and this influence is evidently cumulative. The longer the hot dry 
weather continues, the more potent is it to raise the surface temperature of the water, 
the diminished influx of fresh water being more than made up for by the enhanced 
temperature of the affluents. 

Trip XI., July 1887. — This was a short trip, confined to the West and Central Arran 
Basins and Loch Fyne. It only occupied three days, July 6th to 8th, and was twenty- 
two days later than the June trip. The weather of July, as a whole, was almost as much 
above the average with regard to air-temperature as that of June had been. On the 
cruise, each day was calm; or with very light breezes ; the 6th was dull and showery, 
the other days bright and warm. On this occasion, in the Central Arran Basin, an effect 
common on all calm summer-days was exceptionally well developed. The air blowing 
as a gentle breeze off the land, swept across the water in hot puffs, laden with the scent 
of heather, which could not be perceived at all in the perfectly calm intervals between 
the breezes. The surface temperature of the water averaged about 56°, in Loch Fyne 
exceeding 60°. The water coming in from the Channel had the temperature of 56° on the 
surface and 50° at the bottom on the outer edsje of the Great Plateau in 30 fathoms. In 
the West Arran Basin it was evident that this warm water was doing more than surface- 
heating to warm up the lower layers. The deeper layers of Loch Fyne were, as usual, 
the coldest, but were heating uniformly, showing none of the eccentricities of the 
previous summer. 

In the course of this trip a number of experiments were made on the rate of descent 
of the brass messengers used to reverse thermometers, and on the correction to be applied 
to thermometers read at higher temperatures than those at which they were reversed. 
These results are treated of at pp. 7-8. 

From July 12th until August 12th I was engaged in a special research for the Fishery 
Board for Scotland into the physical condition of the fishing-grounds on the north-west 
coasts of Scotland. I made observations on July 13th on Loch Torridon from H.M.S. 
"Jackal," and found the water in the lower loch to vary from 56° on the surface to 49° 
at 65 fathoms. In the more isolated upper loch, the surface temperature was 61°, and 
that at 45 fathoms 51°. On the following day, observations made in the Minch 



CLYDE SEA AREA. 25 

between Loch Torridon and Stornoway gave 53°'3 for the surface, and 47°'8 at 85 
fathoms. Thus although in that channel there are strong tidal currents, the typical 
mixing of the whole mass of the water found in the North Channel did not occur. 
This work was fully reported on in the Sixth Annual Report of the Fishery Board for 
Scotland for the year 1887, Appendix C, and a summary of the conclusions was 
published, under the title " Sea-Temperatures on the Continental Shelf," in the Scottish 
Geographical Magazine, iv. (1885) 544-549. 

Trip XII., August 1887. — During the month of August 1887, Dr Murray made a 
series of temperature soundings in the Clyde Sea Area, from the 6th to the 9th, doing all 
parts except Loch Fyne, and from the 12th to the 17th, completing Loch Fyne 
and the Arran Basin. Viewed as one trip, this would give an interval of 35 days since 
the last. 

The air-temperature for August was the average for that month, and thus showed a con- 
siderable falling off from July. The 6th was calm ; on the afternoon of the 7th a westerly 
gale sprang up, shifting to north-west and blowing strongly on the 8th, and to north- 
east, dying away on the 9th. For the rest of the time the wind was light and variable. 
Rapid warming had taken place in the shallow lochs and estuary, and in every part of the 
Area the water-temperature was 4° or 5° higher than in August 1886. The Channel was 
occupied by a homothermic mass of water at 55°'3. At the same date my observations 
on H.M.S. "Jackal " showed that in the open Atlantic west of St Kilda the surface tempera- 
ture was 57°, at 30 fathoms 55°'l, and at 100 fathoms 48°. On that occasion I found 
that the water of the North Atlantic was, speaking roughly, of uniform salinity, but that 
it consisted of three horizontal layers of different temperature. The first was a 
homothermic layer at 56°, extending from the surface to 25 fathoms ; this was succeeded 
by a zone of rapid change of temperature about 15 fathoms thick, under which there 
was a homothermic mass of at least 60 fathoms of water at a temperature between 48° 
and 49°. It may not be too much to suppose that this superficial mass of warm water 
represents the Gulf Stream drift ; at anyrate, it is certainly the warm surface water driven 
in toward the land by prevailing westerly wind ; and as the upper homothermic zone 
deepens toward shore, and is stirred throughout its whole extent in passing through tide- 
ways, it appears that the North Channel is usually fed with surface water of the ocean, a 
fact which would largely serve to account for its being warmer than the Clyde Sea Area, 
even in summer. 

On this occasion the warm water pouring across the Great Plateau was obviously at 
work warming the deep basins, the coldest parts of which lay at their upper ends. The 
Dunoon Basin showed a patch of central heating separating cooler water which lay to the 
north and to the south. This effect is probably accounted for by the current of warm 
water sweeping in at right angles from the estuary. The coldest regions were naturally 
the deep lochs : the bottom temperature of Loch Fyne was 45° "2, with no trace of the 
intermediate minimum which kept the bottom water from rising above 44° '2 a year before ; 
that in Loch Goil was 45°"4, contrasting with 43°'l in the previous August. 

VOL. XXXVIII. PART I, (NO. I). D 



26 DR HUGH ROBERT MILL ON THE 

Trip XIII., September 1887. — With its central day 47 days after that of August, 
this trip lasted from September 20th to 30th, with the exception of the 25th, 26th, and 
27th, when a break-down of the "Medusa's" machinery and other causes prevented observa- 
tions from being made. This was the last trip on which I made the observations 
personally, and the last also on which the density of the water was determined. (Part 
II. pp. G 8 4-6 8 5.) 

The temperature for August had been normal over the Clyde Sea Area, and that for 
September about 1° below the seasonal average. The early part of September was stormy, 
with frequent south-westerly gales ; but during the earlier part of the cruise (19th to 
24th) there was an anticyclonic calm, with very light breezes and haze. The 26th and 
27th were characterised by strong winds from N.W. or S.W. ; the 28th, when Loch 
Strivan was visited, was calm, with low barometer and a northerly air ; while on the 29th 
and 30th, the Gareloch and Dunoon Basin were studied amidst heavy squalls from the 
north-east. 

During this trip special attention was given to the condition of the water in the East 
and Central Arran Basins, several cross-sections being run in order to bring out the effect 
of the proximity of land. 

The surface water was everywhere beginning to cool, although heat was still being 
propagated downward in all parts of the Area. Observations by Dr Murray from the 
" Medusa " in the Sound of Mull, and off Ardnamurchan Point in the open Atlantic, showed 
a uniform temperature of 57° '3 from surface to bottom, where the depth exceeded 100 
fathoms, on September 4th. In the Channel the average temperature throughout the whole 
depth was 56° on September 21st ; over the Great Plateau itself it was 55° ; and practically 
the whole mass of the Area was over 50°. The only tracts where the temperature was 
lower were the deep loch basins (Loch Fyne and Loch Goil) and the deepest part of the 
Central and Eastern Arran Basins below 60 fathoms. The deep water of the Area was 
at no previous time, nor on any subsequent occasion, so warm as during this trip, which 
may be taken as representing the maximum storage of heat. The observations early 
in the month on Loch Ness and Loch Morar showed that the minimum temperature at 
the bottom of these fresh-water lakes was 42°*1. 

From October 1887 to October 1888 the "Medusa" was at work on the Clyde Sea 
Area or in the northern lochs almost continuously, and results of great interest were 
obtained in each of the separate divisions of the Area. The continuous method of work- 
ing, although of the utmost service in elucidating the changes in progress in different 
basins (under the head of which they will be considered), was not so well adapted to bring 
out the general character of the Area as a whole at definite periods, separated by approxi- 
mately equal intervals of time. These observations form the subject of a special discussion 
by Dr Murray on the effect of wind in producing temperature changes in sea and fresh- 
water lochs, published in the Scottish Geographical Magazine for 1888, vol. iv. p. 345. 
They are grouped together in what follows into a series of "trips" more or less com- 



CLYDE SEA AEEA. 27 

pletely covering the Area, but individually occupying a considerably longer time in 
doing so than was taken by the thirteen trips already touched upon. 

Trip XIV., November-December 1887. — From September on to the end of 
the year the mean temperature of the air over the Clyde Sea Area was considerably 
below the average for the season, contrasting in this respect with the abnormally mild 
autumn and early winter of 1886, and serving to accelerate the process of cooling-down 
from the great warmth of the summer maximum. The trip was in two parts. The first, 
November 5th to 8th, was devoted to Loch Fyne. The weather was calm on the 5th ; 
on the 7th, stormy, with a fresh breeze from the north-east blowing down the loch, and 
producing very marked changes of temperature; and on the 8th, a light breeze from E.S.E. 
The second part, from November 29th to December 10th, took account of all the remain- 
ing divisions of the Area. The first day was calm. From December 2nd to 8th the wind 
blew freshly or strongly from the west, south-west, or south. On the 9th and 10th 
it was light and northerly. At the bottom of Loch Fyne the temperature was 45°"5 ; 
at the bottom of Loch Goil 49°*4, the highest ever found there. In the Channel the 
water was at 49°' 8, showing rapid cooling since September. Surface temperature 
diminished rapidly landward, and came to a minimum of 42° in Loch Goil. The surface 
was everywhere colder than the deeper layers, the vertical curves everywhere showing 
the typical negative slope of winter. The warmest water was found, curiously enough, 
in Loch Strivan, where all beneath 5 fathoms was at 50°"1. 

Trip XV., December 1887 '-January 1888. — This trip extended from December 
15th to January 8th, and during it particular attention was given to the conditions of 
the Upper Basin of Loch Fyne, with special reference to the influence of wind. All 
parts of the Area were visited. December was considerably below the average of the 
season with regard to air-temperature. During the cruise all varieties of weather were 
found. It commenced in a calm, followed by variable airs, which on the 17th developed 
into a heavy gale from the west and north-west, blowing across Loch Fyne. On the 
18th there were heavy squalls from the north-west, but the rest of the month had only 
light winds. On the last day of the year, when the Great Plateau was being examined, the 
breeze blew fresh from the west, changing to S.S.E., and increasing in force on January 
1st. The last week was characterised by light winds, usually from a southern quarter. 
No observations were made on this trip in the Dunoon Basin, or the lochs with which 
its northern end communicates. 

The water of the North Channel was at 47° "3 ; that in the middle of Loch Fyne, 
although sandwiched between colder layers, remained the warmest (48°'5) in the Area, 
so far as the observations could show. Except in Loch Fyne, which was warmer, the 
temperature of the Area at five fathoms averaged 45°, and at 30 fathoms a little over 
46°, showing how rapidly surface-cooling was at work. It is noticeable that, as in the 
previous year, the Channel temperature remained higher than that of the partially 
enclosed waters inside the Great Plateau. 

Trip XVI., January 1888. — The month of January was, like February of the 



28 DR HUGH ROBERT MILL ON THE 

previous year, distinctly above the average with regard to air-temperature. Only a 
few observations were made, and these only in the southern part of the Area, 
between the 18th and 20th, when light winds from east and south prevailed, on the 
27th, during a heavy northerly gale, and the 30th, in a dead calm. The temperature 
of the few stations examined on both occasions was found to be about a degree lower 
than during Trip XV. Advantage was taken of the storm, on the 27th, to investigate 
the action of wind in Loch Strivan. 

Trip XVII., February 1888. — Observations were made in the Gareloch on the 9th 
and 10th in heavy squalls and a prevailing north-westerly wind. From the 11th to 
15th the weather was fine, with a very light northerly wind, on the 15th the wind was 
westerly, and on the 16th a light air from the south. On the 17th, the last day of the 
trip, the wind rose to a gale from the north-east. The mean air-temperature of 
February was fully 2°'5 lower over the Clyde Sea Area than the normal, thereby 
contrasting with the exceptionally mild February of 1887, and approximating to the 
great cold of February 1886. 

In the Channel the water had a temperature of 44° *8, but for the rest of the Area the 
average was about 44° '3, with little change on account of depth in the more open basins. 
At the head of the Arran and Dunoon Basins 45° '0 was found at the bottom, but the 
warmest water occurred, as usual, in Loch Goil, which below 20 fathoms was within 
0°'2 of 46°, and in Loch Fyne, where a well-marked intermediate maximum, over 46°, 
occurred between the depths of 3 and 20 fathoms. 

The general condition was a reversion toward the simple arrangement of temperature, 
homothermic as regards both depth and surface, which is characteristic of the spring 
minimum. The curious fact, several times noticed before, that the whole mass of the 
great Arran Basin was colder than the water of the Channel or that of the enclosed 
lochs was again brought out, although the Channel was colder than usual proportionally. 
In fact, at this period, or during the rise of temperature in summer, a rough map of 
the configuration of the Sea Area might be sketched out by paying attention to 
the temperature alone. 

Trip XVIII. , March 1888. — Observations were made on February 28th and March 
1st, in calm weather, with a light north-easterly air ; and also on the 6th, 8th, and 10th of 
March, with equally light south-westerly wind. The Dunoon Basin and Great Plateau 
were alone studied in any detail, one observation each being also made at Skate Island 
and Strachur. 

The water coming in from the Channel was rather under 43° in temperature, and in 
crossing the Plateau it sank to 42°, being as cold as had ever been observed in that 
position. The mass of the Arran and Dunoon Basins, so far as observations went, was 
warmer, though showing a steady cooling throughout since the previous trip. The 
Dunoon Basin showed greatest cooling at its seaward end, as if the Channel water were 
chilling it — a mode of cooling strongly confirmed by the nearly uniform distribution of 
temperature from surface to bottom and the absence of any marked surface-cooling. At 



CLYDE SEA AREA. 29 

Knock the temperature of 44° was reached at 30 fathoms, the surface being at 43°'2, and 
at Dog Kock at 15 fathoms, the surface being at 43°. Similar evidence of mass-cooling was 
brought forward by Trip No. VII. in February 1887, when, despite higher temperatures, 
the general distribution of warmth in the water was very similar. 

Trip XIX., March 1888.— To complete the resemblance between the early Spring of 
1888 and that of 1886, the air-temperature for March was even lower with regard to the 
average than that of February, the mean temperature of the air over the Clyde Sea Area 
being the same (37°'5) for the two months. This trip lasted from March 17th to 31st, 
with a break from the 24th to the 26th inclusive, and a good general survey of the whole 
Area was made. The weather varied greatly, the wind being, on the whole, northerly or 
easterly, and usually light. On the 19th there was a stiff easterly wind with squalls, on 
the 21st a strong breeze from N.N.E., on the 23rd a fresh north-easterly breeze, sinking 
to a calm, and on the 28th a gale from the north-east and east, accompanied by a 
snowstorm. 

In spite of the short interval between this trip and the last, there had been a well- 
marked and general fall of temperature in the water to the extent of nearly 2° on the 
average. The deep lochs alone retained water exceeding 43° in temperature, the water 
in the Channel was just at 43°, in the Arran Basin it scarcely exceeded 42° on the 
average, and was almost homothermic. Everywhere the conditions of the Spring 
minimum were being closely approximated to, but the temperature was still evidently 
falling. The whole Dunoon Basin ranged from 42° to 43°. In Loch Goil there was an 
intermediate maximum rather over 43° '5, and in Loch Fyne the maximum temperature 
of the Area, 44°*1, occurred on the bottom. The Gareloch was in every way the coldest 
division, averaging barely 42°. 

Trip XX., April 1888. — Observations were made on April 3rd, 6th to 10th, and 
14th, either in dead calm weather or with light breezes from a northerly quarter, except 
on the last day, when there was a light southerly air. The air-temperature for April 
was still below the average for the season. 

The water-temperature, so far as the few observations' which were made can show, 
appeared to be rising after the minimum which must have occurred between this trip and 
the previous one. In the Dunoon Basin the average temperature of each vertical 
sounding was about 42° # 5, and in the Arran Basin probably about 42° *3, while in every 
case the surface was warmer, ranging between 43° and 44°. It is unfortunate that more 
complete observations were not made at this date, as it seems to have been the nearest 
approach to a return to the conditions found in April 1886, when the systematic work 
on the Clyde Sea Area was commenced. On that occasion only there was no indication 
whatever of any physical difference due to configuration. On the present trip the single 
sounding in Loch Fyne off Strachur showed the minimum temperature of 43° '0 on the 
bottom, while at similar depths in the Arran and Dunoon Basins the temperature was 
42°, or a little less. 

This trip is interesting, because the observations are sufficient to enable a comparison 



30 DR HUGH ROBERT MILL ON THE 

to be made with the state of matters in the northern lochs of the West Coast visited by Dr 
Murray in the "Medusa" from April 20th to May 23rd. On April 20th a sounding off Jura 
in 103 fathoms gave an average temperature of 43°'3, and on the 21st, somewhat farther 
north, in a slightly deeper place, the average vertical temperature was 43°"6. Off Kerrara, 
on the 23rd, the water, 57 fathoms deep, was perfectly homothermic at 43°*5, and on the 
22nd, in the Firth of Lome (114 fathoms), there was a homothermic temperature of 45°; 
but on May 9th the constant temperature was 44°*2. These observations were made in 
places fully open to the sweep of Atlantic currents, and it is curious to notice that the 
water was warmer in the more northerly positions. The mass of Loch Linnhe, Loch Aber, 
and Loch Sunart had a uniform temperature of about 44° "5 ; and Loch Etive, which was 
very carefully studied on two separate occasions during the trip, showed still higher 
temperatures ; maximum readings of 49 o- were found at 26 fathoms in the deepest part, 
and a minimum of 44° - 6 on the bottom. Nowhere were readings found approximating 
to the conditions of the Clyde Sea Area, and the suggestion arises that the broad shallow 
plateau across the entrance to the Area must, about the period of the annual minimum, 
exercise an independent chilling influence on the inflowing water passing over it. 

Trip XXI, June 1888. — From the 2nd to the 11th of June observations were made 
on six days, most of the time being spent in a very detailed examination of the Gareloch 
and Loch Strivan, although Loch Fyne and part of the Arran Basin were also visited. 
May had been a month of normal air-temperature, but June was rather below the 
average in that respect. The wind was light as a rule, but on the 5th it blew freshly 
from the south-east ; on the 7th, when the Gareloch was under investigation, it was 
easterly, and sometimes very strong, blowing transversely to the loch. On the 9th, 
when Loch Strivan was similarly examined, the wind varied from west to north-west, 
and rose at times to a fresh breeze, blowing, on the whole, down the loch. 

Dr Murray dealt fully with the observations in his article in the Scottish Geo- 
graphical Magazine already cited. They showed, taken generally, that rapid warming 
was in progress, the Arran Basin having warmed up to an average vertical temperature 
of 44°"5. This June was much colder than that of 1887, although warmer, so far as 
regards the deeper water in particular, than that of 1886. It is interesting to notice 
that there is no trace of the intermediate minimum in Loch Fyne which was so 
prominent and puzzling a feature of 1886. 

Trip XXII., August-September 1888. — Observations were made on twelve days 
between August 14th and September 8th. The summer had been the coldest of the three 
during which observations were made, the air-temperature being as much below the 
average for the three months June, July, and August as it had been above the average 
for the same months in 1887. During the observations the weather was, as a rule, 
warm and calm, strong wind being experienced on only two occasions, August 27th and 
September 6th, both times a stiff breeze from the south-west. Surface temperature was 
highest in the lochs, reaching 60 o, in Loch Fyne, and lowest in the East Arran Basin, 
where it was 55°*0. The average temperature of the vertical sections was, as might be 



CLYDE SEA ABEA. 31 

expected, highest in the open basins and lowest in the enclosed lochs. No observations 
were made on the Great Plateau or in the Channel. The arrangement of temperature 
in all the parts examined was similar to that of the two previous Augusts. 

Trip XXIII., October 1888. — Observations were taken in the landward part of 
the Area, from October 16th to 25th, in calm weather, and these admit of comparison 
with observations made on the West Coast of Scotland, further north, on the 5th and 
6th. August and September had been slightly below the average with regard to air- 
temperature, but October was a normal month. 

The water-temperatures observed showed that surface- cooling had set in. This did 
not always show itself by the surface layer being colder than that immediately below, 
but rather by the formation of a homothermic body of water at about 50°, 15 fathoms or 
more in thickness, beneath which there was a steady fall of temperature to 44° '2 in Loch 
Fyne, 45°'0 in Loch Goil, and 48°'6 in the deepest part of the Arran Basin. The 
Dunoon Basin, Loch Strivan, and the Gareloch were entirely occupied by the warm 
surface stratum, which reached the depth of over 50 fathoms in some places. 

A sounding of 73 fathoms in the Sound of Jura on October 1st, and another of 45 
fathoms in the Firth of Lome on the 9th, showed that 53°*5 was the uniform temperature 
from surface to bottom of the margin of the ocean. In Loch Aber a temperature of 53° 
prevailed to the bottom, and Loch Etive was also much warmer than the lochs of the 
Clyde Sea Area. 

General Results of the Trips. — It was by an accident of a very remarkable kind 
that the thermal condition of the water on Trip I. should be so uniform, both in super- 
ficial, and vertical distribution as to arouse no suspicion whatever of the true 
determining causes of temperature change. On every other occasion during the three 
and a half years covered by the observations, the importance of the physical configura- 
tion of the Area was strongly, or at least clearly, marked. Broad distinctions were 
indicated between the different natural divisions of the Area which, while originally 
marked off with regard to configuration alone, were found to have a distinct thermal 
individuality. Arranged according to iD creasing restriction in communication with the 
ocean, these divisions are the Channel, Great Plateau, Arran Basin, Dunoon Basin, Loch 
Strivan, the mountain lochs (Loch Fyne and Loch Goil). The Gareloch occupied a 
place by itself, or rather along with the Estuary, as showing the influence of the land 
in an exaggerated manner. Speaking generally, the more completely isolated each 
natural division was, the more slowly were thermal changes carried on as the seasons 
succeeded each other, and the lower was the mean annual temperature. 

Thermal Conditions of the Divisions of the Clyde Sea Area. 

The remainder of this memoir is occupied with a discussion of the conditions of each 
of the natural divisions carried as far as seemed reasonable in each case, and finally 
by a general statistical summary of the whole work. 



32 



DR HUGH ROBERT MILL ON THE 



The observations made in the Estuary were too few and scattered to be worth 
separate consideration, while those in Campbeltown Loch, the Holy Loch, Loch Long, 
Loch Ridun, and the Kyles of Bute are also not considered, partly because the positions 
were not characteristic, and the same order of phenomena was better illustrated by one 
of the other divisions which was fully treated. 

The North Channel. 

In some respects the Channel is the most important of the physical regions studied, 
and of all parts of the Area it is the one where observations should have been made 
most frequently. On account of the small size of the " Medusa," and the rough state of 
the water caused by tidal races and ocean swell, it was only on a comparatively small 
number of occasions that full observations could be secured. An effort was made as a 
rule to obtain soundings off the Mull of Cantyre, where the Atlantic water is quite 
unaffected by the shore. When this was impracticable, it was often possible to observe 
off Deas Point, about 1\ mile from land, but when, as was usually the case in winter, 
it was unsafe to pass through Sanda Sound in the " Medusa," observations had to be 
made at a point about 5 or 6 miles south of Sanda. Here the water was over 50 fathoms 
in depth and fairly beyond the Great Plateau. In the summary of observations given 
in the table, these three stations are indicated respectively by the initials C, D., and S. 

Table V. — Temperature Observations in the Channel. 



No., . . 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 


14 


15 


16 


17 


18 


Date, . . 


16.4.86 


16.4.86 


19.6.86 


12.8.86 


22.9.86 


25.12.86 


30.3.87 


4.5.87 


5.5.87 


17.6.87 


18.8.87 


21.9.87 


8.12.87 


31.12.87 


16.2.88 


17.3.88 


21.3.88 


31.3.88 


No.of Pts. 


9 


9 


10 


13 


10 


6 


6 


9 


7 


12 


6 


6 


9 


6 


9 


6 


9 


6 


Temp., . 


42-0 


42-0 


47-4 


52-4 


54-5 


48-5 


44-3 


45-8 


45-7 


48-8 


55-3 


55-9 


49-9 


47-3 


44-8 


43-0 


43-0 


42-9 


Slope, 


+0-0 


+ 0-6 


+0-4 


+ 0-2 


o-o 


-0'2 


+ 0-3 


+ 0-1 


+0-7 


+2-3 


+ 0-0 


-0-1 


-o-i 


-o-i 


-0-4 


-0-1 


-0-4 





Depth, . 


44 


68 


34 


50 


65 


43 


49 


60 


44 


57 


48 


45 


49 


48 


64 


48 


62 


34 


Place, . 


S 


C 


D 


D 


C 


S 


S 


C 


S 


S 


C 


S 


S 


S 


C 


D 


S 


C 



The number of observations for each sounding is mentioned in the above table as 
" No. of Pts." Temp, signifies the mean temperature of the vertical section in degrees 
Fahrenheit. " Slope " is the range of temperature between the surface and bottom layer 
of 5 fathoms thick. "When the surface is warmer, the slope is positive ; when the surface 
is colder, negative. Depth is given in fathoms. 

The striking physical feature of the Channel is the tumultuous rush of the tides 
(see Part I. p. 653). This appears, from the discussion both of salinity and of tempera- 
ture, to effect a thorough mixing of the water from bottom to surface ; a condition 
particularly well brought out by the curves of vertical distribution of temperature, which 
are practically homothermic at all seasons of the year. Of the eighteen soundings in water 



CLYDE SEA AREA. 33 

for the most part over 50 fathoms in depth, the difference in the mean temperature of 
the surface and bottom layers of 5 fathoms each exceeded half a degree on three 
occasions only, and was less than quarter of a degree on eleven occasions. Four times 
no difference in temperature with depth could be detected. 

Fig. 4, Plate XXIII. , reproduces several of the vertical temperature curves, all of which 
show a practically homothermic condition. In No. 2 the dotted part represents the surface 
temperature found off the Mull of Cantyre at 12 h .10 ; below 3 fathoms the curve coin- 
cides exactly with that found south of Sanda at 10 h .50, showing that a perfectly homo- 
thermic body of water rilled the whole extent of the Channel. The tide had turned 
and was beginning to run westward when the " Medusa" was off the Mull of Cantyre, 
and on the return journey the tidal stream was so strong that the vessel was scarcely 
able, going 6 knots, to make head against it. Surface temperature observations were 
taken every few minutes, and the results were curiously irregular. Patches of water at 
45°*0 were once or twice passed through, but the prevailing temperatures ranged from 
42° '0 (the minimum) to 42° '3. Great patches of oilily-smooth water were interspersed 
amongst the generally rippled surface, and on the whole these seemed to be a fraction 
of a degree cooler than the rippled surface. The smooth patches suggested the idea of 
up welling water from beneath, possibly of greater density and different surface-tension 
from the rest, forming calms in the same manner as a film of oil does. The late 
Professor James Thomson suggested, in referring to this observation, that the accumula- 
tion of floating objects along the lines of junction of masses of water moving vertically 
in opposite directions, on account of tidal disturbance, would act as floating break- 
waters or dampers for the small ripple undulations.* On the same afternoon the 
temperature between Sanda and Pladda, on the Great Plateau, was found by two 
different soundings to be 45° '3 on the surface, 43° at 5 fathoms, and 41°*4 at the 
bottom in 25 fathoms, the low temperatures being obviously due to overflow from 
the Arran Basin within, in which the whole mass below 15 fathoms was colder than 42°. 
Whether the isolated warm surface patches in the Channel were due to direct heating 
by the very strong sunshine or to isolated flakes of surface water from the Plateau, or the 
narrow beach of Cantyre, whirling seaward, does not appear. It is quite certain, however, 
that there was nothing of the nature of a continuous warm upper layer. Whether 
heating or cooling, the water of the Channel changed its temperature homothermically, 
and the straightness and parallelism of the vertical curves at all seasons, points 
unmistakably to continual agitation and thorough mixture by the tidal currents. 

The one exception is observation No. 10, on 17th June 1887, when the superficial 
5-fathom layer averaged 2°*3 warmer than the bottom layer of 5 fathoms, the whole 
curve having a distinct positive slope. On that occasion the very hot weather appears 
to have produced a strong effect on the upper layers. This observation was made south 
of Sanda, the anticyclonic haze making it impossible to reach the more open water. But 
even in this case the surface water was more than five degrees colder than the surface 

* Miller, " Tlie Clyde from Source to Sea," p. 293. 
VOL. XXXVIII. PART I. (NO. 1). E 



34 DR HUGH ROBERT MILL ON THE 

water of the Plateau and neighbouring parts of the Arran Basin, showing that by no 
means inconsiderable mixing had taken place. In the deep water outside the Plateau 
there appears to be little variation in temperature in different places. On September 
22nd, 1886, from Mr Matheson's yacht "Oimara," the temperature off the Mull of Cantyre 
was found to be uniformly 54°*5 in 65 fathoms. Off Corsewall Point, on the eastern edge 
of the Channel, 30 miles S.E. of the Mull, the mean temperature in 46 fathoms was also 
54°"5, the upper 20 fathoms being at 54°*3, the lower layers warming up to 54 0, 8. On 
the same occasion, in 70 fathoms off the Maidens on the Irish coast, 20 miles south of 
the Mull of Cantyre, there was uniform temperature of 55° '1 from surface to bottom. 
This shows that the Channel type of curve is not confined to the vicinity of the Mull of 
Cantyre. As soon as the shallow water of the Great Plateau was entered on, the 
surface temperature fell, the winter condition being in course of formation. 

During May and June 1887 several serial temperature soundings were made by the 
Fishery cruiser " Vigilant, " # in about 40 fathoms, off the southern end of the Outer 
Hebrides. The curves expressing these showed, as a rule, a uniform positive slope from 
surface to bottom, the change of temperature being about 1° F. per 10 fathoms. The 
regularity of these curves is very remarkable, and it is by no means improbable that the 
Channel curve is derived from this form by thorough mixture of the water. My ob- 
servations on H.M.S. "Jackal" to the west of Lewis in July and August 1887 t suggested 
a different probable cause, already referred to (ante, p. 25). In the Minch T found 
curves of nearly uniform positive slope similar to those obtained by the " Vigilant " in 
June (A, fig. 5, Plate XXIII. ), but in the open Atlantic, west of Lewis, the typical form 
was that shown at B (fig. 5), and, as already explained, I think it probable that the 
upper layer at nearly constant temperature is driven by the surface drift against our 
coasts, and so enters the Channel. Between the Inner and Outer Hebrides, this water 
may be supposed to be embayed and brought under the influence of local heating. 
The curve B is, I believe, the typical form for the upper layers of water in the open ocean, 
at least near lee shores. It may be viewed as a triply compound curve, uniting the 
homothermic, inverted, and paraboloid positive types. 

Seasonal Change of Temperature in the Channel. — A diagram (PI. IV. fig. 7) was 
constructed in order to show the variation of temperature in the Channel with regard to 
depth and time. This shows the isotherms as almost exactly parallel, straight, vertical 
lines, crowded together at the times of heating and cooling, spread rather farther apart 
at the maxima, and widely spaced at the minima. The diagram, being coloured on the 
principle already mentioned, shows a series of vertical strips of colour, the summer of 
1887 showing much deeper tints than that of 1886, but the general order of change is 
the same for both. A great widening of the isotherms in June, and a corresponding 
crowding in July and August, 1887, is probably an effect due to incomplete data. 
Indeed, the diagram is largely hypothetical as regards the spacing of isotherms inter- 

* Eleventh Annual Report of Fishery Board for Scotland for 1892. Part III. 
t Sixth Annual Report of Fishery Board for 1887. 



CLYDE SEA AREA. 35 

mediate between those fixed by observation ; but the fixed lines prevent the error from 
being great at any point. Since the isotherms are vertical, their values show not only 
the temperatures of surface and bottom water, but the mean temperature of the whole 
mass of water at all times from April 1886 to May 1888, a period comprising two 
maxima and three minima. From this diagram of continuous range, checked by constant 
references to the actual means given in the table, a curve (fig. 6, Plate XXIII.) was 
drawn, showing the variation of the temperature of the mass of water, the position of 
each degree being fixed for time by the diagram. The curve, slightly smoothed, may be 
taken as fairly representative of the actual order and amount of temperature changes. 

From a minimum of 42° on April 16th, 1886, the temperature of the water mounted 
steadily to a maximum of 55° on September 10th, a rise of 13° in 147 days, or at the 
rate of almost 0°"090 per day. The rate of fall, at first comparatively rapid, fell off after 
the end of September, but became quicker again after January 20th, and the temperature 
reached a minimum of 43°*8 (or possibly lower) on February 28th. This was a loss of 
11°'2 in 171 days, at the average rate of 0°'065 per day. The temperature continued 
to rise in the spring of 1887, at first slowly, and then more rapidly, reaching a maximum 
of 5 6° "2 on September 5th. Throughout the rise the water was on the average two 
degrees warmer than at the same period of the previous year. The period from Spring 
minimum to Autumn maximum was 189 days, and the range of temperature 12°*4, the 
rate of warming thus averaging only 0°*065 per day, the same as the rate of cooling 
during the previous winter. The fall of temperature in the winter of 1887 was much 
more uniform than in 1886. Up till December 10th, 1887 remained warmer, but after 
that date it became colder than 1886, reaching a minimum of 42°*6 on April 10th, 1888. 
The interval from Autumn maximum to Spring minimum was on this occasion as 
much as 217 days, and the total cooling 13°"6, an average loss of 0°*062 per day. In 
1886, the period of cooling was 16 per cent., and in 1887, 15 per cent, longer than the 
period of heating. 

The mean temperature of the water for 1886 (interpolating probable values for the 
first three months) must have been about 48° '2, and the mean temperature of the air 
at the Mull of Cantyre lighthouse for the same period was 46° '5. The mean water- 
temperature for 1887 was 49° # 3, and the air-temperature 47°'6 ; the water thus appearing 
to be on the whole about 1°*7 warmer than the air. This shows that the water of the 
Channel is on the whole a warming agent during the whole year, and confirms the Gulf 
Stream drift theory of its origin. 

The comparison of air and water temperature in detail brings out several points of 
interest. The range of air-temperature is greater and its phase earlier than that of water- 
temperature. Both years showed similar relations. The air curve rose much more steeply 
than that of the water, which it crossed upward in April close to the water minimum, 
and came to a maximum in July, from five to six weeks before^ the water maximum. 
Descending, the air curve cut the water downward at its maximum, cooled much more 
rapidly, and came to a double minimum in December and March, the former being the 



36 



DR HUGH ROBERT MILL ON THE 



lower in 188G, the latter in 1887. Taking the elate of mean air minimum to be the 
middle of February, it appears about six weeks earlier than the water minimum. The 
period of heating for the air is shorter than that for the water in comparison with the 
period of cooling. In 1886 the period of air-cooling was 24 per cent., and in 1877, 
32 per cent, longer than that of heating. 

The rate of change of temperature in the mass of the water is also a matter of interest, 
considered with regard to its fluctuations with time. 



Table VI. — Rate of Change of Temperature in the Channel. 



Calculated from Curve. 


Calculated from Observations. 


Period. 


Days. 


Change of 
Temperature. 


Do. 

per Day. 


Periods. 


Days. 


Change of 
Temperature. 


Do. 
per Day. 


1886. 




° F. 


F. 


1886. 








April 16-30, 


15 


+ 1-1 


+ 0-074 


April 16-June 19, . 


64 


4-5-4 


+ 0-084 


May 1-31, . 


31 


+ 2-9 


+ 0-094 










June 1-30, 


30 


+ 2-7 


+ 0-090 










July 1-31, . 


31 


+ 2-6 


+ 0-084 










Aug. 1-31, . 


31 


+ 3-1 


+ O-IOO 


June 19-Aug. 12, . 


53 


+ 5-0 


+ 0-094 


Sept. 1-30, 


30 


-1-4 


- 0-047 


Aug. 12-Sept. 22, . 


41 


+ 2-1 


+ 0-051 


Oct. 1-31, . 


31 


-2-0 


-0-065 










Nov. 1-30, 


30 


-1-6 


-0-053 








. 


Dec. 1-31, 


31 


-1-5 


- 0-048 


Sept. 22-Dec. 25, . 


94 


-6-0 


- 0-064 


1887. 








1886-87. 








Jan. 1-31, . 


31 


-2-0 


-0-065 










Feb. 1-28, . 


28 


-2-2 


-0-078 










March 1-31, 


31 


+ 0-6 


+ 0-020 


Dec. 25-M'arch 30, . 


95 


-4-2 


- 0-044 


April 1-30, 


30 


+ 1-1 


+ 0-037 


1887. 








May 1-31, . 


31 


+ 1-7 


+ 0-055 


March 30-May 4, . 


35 


+ 1-5 


+ 0-043 


June 1-30, 


30 


+ 3-0 


+ O-IOO 


May 4- June 17, 


44 


+ 3-0 


+ 0-070 


July 1-31, . 


31 


+ 3-7 


+ 0-I20 










August 1-31, 


31 


+ 2-5 


+ 0-083 


June 17 -Aug. 18, . 


62 


+ 6-5 


+ 0-105 


Sept. 1-30, 


30 


-1-1 


-0-037 


Aug. 18-Sept. 21, . 


34 


+ 0-6 


+ 0-018 


Oct. 1-31, . 


31 


-23 


-0-074 










Nov. 1-30, 


30 


-2-7 


- 0-090 






. 




Dec. 1-31, . 


31 


-2-6 


- 0-084 


Sept. 21 -Dec. 8, . 


78 


-6-0 


-0-077 


1888. 
















Jan. 1-31, . 


31 


-2-0 


- 0-065 


Dec. 8-31, 

1888. 


23 


-2-6 


-0-113 


Feb. 1-28, . 


28 


-1-5 


-0-054 


Dec. 31-Feb. 16, . 


47 


-2-5 


-0-053 


March 1-31, 


31 


-1-2 


-0-037 


Feb. 16-March 17, . 


29 


-1-8 


— 0-062 


April 1-30, 


30 


+ 0-2 


+ 0-007 


March 17-21, . , . 


4 


o-o 


o-ooo 










March 21-31, . 


10 


-o-i 


- O-OIO 



Table VI. gives the mean monthly rate of change calculated from the temperature 
curve, and also the more irregular deductions for the intervals of time between actual 



CLYDE SEA AREA. 37 

observations. The latter are used only to check the former. Plotting the rate of change 
per diem ± with the amount of change as ordinates and time as abscissas, a curve of 
great interest is produced. This curve (Plate XXIII. , fig. 6) shows that, starting with the 
spring minimum, the rate of warming is zero, but immediately afterward it increases, at 
first rapidly, then more gradually, until it reaches a maximum just before the seasonal 
maximum of temperature. At that moment the rate drops to zero, and cooling com- 
mences, at first rapidly increasing, then continuing steadily until the eve of the spring 
minimum, when the rate of cooling drops off and heating begins. For 1886 the 
maximum monthly rate of change per day was + 0°*104 in August, and — 0°*067 in October. 
In 1887 it was -0°'077 in February, +0°'120 in July, and -0°-090 in November. 

Thus, while the temperature was rising rapidly at the time of the maximum of air- 
temperature, the water was gaining heat throughout at the rate of 1° in 8*3 days in 1887, 
and 1° in 9 '6 days in 1886. When cooling most rapidly in October 1886 it lost 1° in 
15 days, and in November 1887 it lost 1° in 11 days. Storing neat thus appears to be 
a more rapid process than parting with it. In the case of water this is probably due to 
solar radiation heating it throughout from surface to bottom, whereas in cooling, water 
radiates heat from the surface only, and the slower processes of convection or even con- 
duction are required to send the heat out of the mass. 

The Great Plateau. 

The Great Plateau is the threshold of the Clyde Sea Area, and over its sill, which 
reaches to within 21 fathoms of the surface at low tide, all exchanges of water between 
the Area and the ocean have to pass. The southern edge of the Plateau is relatively 
steep toward the Channel, but its surface slopes up very gradually to the narrow belt of 
minimum depth. So gentle is the slope that in considering temperature changes the 
whole may be looked on as a uniform level, across which masses of water oscillate with 
the tides between the deep water to north and south. The middle of the northern edge 
of the Plateau runs on to the shore of Arran. Its western edge dips westward into the 
North Channel beyond Sanda, runs up the east coast of Cantyre as far as Davaar Island, 
and in Kilbrannan Sound dips rapidly to the deep water of the West Arran Basin. On 
the east side Ailsa Craig rises rather to the south of the highest part of the Plateau, and 
the slopes are uniform to the coast of Galloway, and northward bordering the East Arran 
Basin in a wide shallow round the shore of Ayr. The deep water of the East Arran 
Basin lies toward the west, much nearer the coast of Arran than that of Ayr, and there 
is a comparatively steep gradient off the island of Pladda at the south end of Arran. 
The water on the Plateau was, in its average condition, just perceptibly less dense than 
that of the Channel, and the surface and bottom salinity were practically equal. 

Observations were made most frequently on the western part of the Plateau, for in 
uncertain weather the deep water of the Channel could be reached best to the south of 
Sanda, and Campbeltown Loch was the only convenient harbour from which to work. 
Distance from any harbour made the number of observations in the south-eastern part of 



*8 



DR HUGH ROBERT MILL ON THE 



the Plateau, about Ailsa Craig, very small. But on the run from Lamlash to Campbel- 
town, which was frequently made, observations were secured pretty often across the 
northern end. The common observing places were (1) to the south-east of Pladda, (2) 
midway between Pladda and Sanda, and (3) to the east or north-east of Sanda. Some- 
times no observations could be made beyond the shelter of the land, and then they were 
usually carried out off Rhuad Point or Davaar Island, near the Cantyre coast, or off 
Bennan Head, in the south of Arran. 

The observations may be grouped for convenience into an eastern and a western set, 
but the locality of each sounding is in each case indicated. Observations made by the 
Fishery Board's cruiser "Vigilant," and discussed by Mr Herbertson and myself in the 
Eleventh Annual Report of the Fishery Board for Scotland, furnished some data contem- 
porary with those of the " Medusa," and supplementary to them. 

Table VII. gives particulars of dates and mean temperatures at stations on the east 
and south-east parts of the Plateau. 

Table VII. — Observations on the Great Plateau (Eastern Side). 



No. 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11* 


12 


13 


14* 


15* 


16* 


17* 


Date. . . . 


20.6.86 


22.9.86 


26.12.86 


5.5.87 


17.6.87 


6.7.87 


21.9.87 


21.9.87 


21.9.87 


21.9.87 


1.10.87 


10.12.87 


19.1.88 


14.2.88 


17.2.88 


26.4.88 


9.5.88 


No. of Points 


5 


7 


4 


13 


9 


13 


7 


7 


4 


4 


6 


6 


6 


5 


5 


6 


6 


Temperature 


48-8 


54-0 


46-3 


45-3 


49-8 


51-5 


55-2 


55-6 


55-3 


557 


53-7 


47-7 


45-3 


44-4 


44-3 


43-7 


44-5 


Slope . . . 


+ 5-3 


-0-8 


+ 0-1 


+ 1-4 
( + -ll) 


+ 4-8 


+ 8-9 


o-o 

(til) 


o-o 


0-1 


-01 


+ 0-5 


o-o 


-0-6 


-1-4 


-1-7 


+ 0-8 


+ 2-1 


Place. . . . 


P 


A 


P 


A-P 


P 


P 


A-P 


A-P 


A 


A-S 


P 


P-S 


A 


P 


P-A 


A.-S 


A 


Depth . . . 


20 


26 


11 


29 


25 


23 


30 


28 


32 


28 


22 


23 


36 


30 


30 


28 


25 



* "Vigilant " Observations. 
P, east or south of Pladda. A, near Ailsa. A-P, between Ailsa and Pladda. A-S, between Ailsa and Sanda. 

With so few data, scattered so irregularly over a long interval of time, it would be 
useless to attempt detailed discussion ; but the general average rate of heating and cool- 
ing of the mass of water may be deduced as in Table VIII., — the wide flat expanse of the 
Plateau allowing one to assume the mean vertical temperature of the station as approxi- 
mately that of the whole q uantity of water in the neighbourhood. 



Table VIII. — Rate of Change of Water- Temperature on the Great Plateau (Eastern Side). 





Period. 


Temperature 
Change. 


Days. 


Mean rate of 
Change per Day. 


Remarks. 


1886 
1887 

1888 


June 20-September 22 
September 22-December It 

June 17-September 21 
September 21-October 1 
October 1-December 10 . 
December 10-January 19 
January 19-February 14 

April 26-May 9 . . . . 










+5-2 
-7-7 

+ 4-5 
+ 5-6 
-1-5 
-4-0 
-2-4 
-0-9 
-07 
+ 0-8 


94 
95 

33 
96 
10 
71 
40 
26 
71 
13 


+ °'°55 
— o - o8r 

+ 0-136 
+0-058 
-0-150 
-0-056 
-o - o6o 
-°"°35 

-O"0IO 

+ o - o6i 


Valueless through lost minimum. 
Probably includes minimum. 



CLYDE SEA AREA. 



39 



Table IX. summarises the observations made on the west and north-west parts of the 
Plateau. 

Table IX. — Temperature Observations on the Great Plateau ( Western Side). 



No 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 


14t 


ist 


15a 


let 


17t 




15.4.86 


16.4.86 


16.4.86 


20.6.86 


12.8.86 


12.8-86 


22.9.86 


18.11.86 


18.11.86 


25.12.86 


10.2.87 


11.2.87 


31.3.87 


22.4.87 


27.4.87 


9.5.7 


10.5.87 


16.5.87 


No. of Points . 


7 


9 


7 


9 


14 


7 


7 


6 


12 


4 


6 


5 


3 


8 


6 


6 


9 


6 


Temperature . . 


42-6 


42-2 


42-8 


48-0 


53-0 


52-8 


54-2 


50-3 


50-0 


46-9 


43-8 


435 


43-5 


44-5 


44-3 


45-6 


45-4 


50-4 




+1-5 


+2-2 


+2-3 


+3-0 


+0-7 


+0-2 


-0-4 


+ 0-2 


-0-2 


-1-4 


-01 


-o-i 


+0-3 


+0-9 


+1-5 


+2-2 


+0.7 


4-1-4 


Placet .... 


S 


S-P 


R 


S-P 


S-P 


S 


S 


S-P 


D 


R 


D 


R 


D 


D 


D 


D 


D 


D-P 




24 


25 


20 


29 


24 


28 


23 


21 


20 


17 


25 


19 


20 


20 


29 


29 


24 


22 



No 

Date . . . . 
No. of Points 
Temperature . 
Slope . . . . 
Placet • • ■ 
Depth . . . . 



18t 


19* 


20 


21 


22 


23 


24f 


25t 


26t 


27t 


28 


29 


30 


31 


32 


33 


34 


35f 


26.5.87 


18.6.87 


6.7.87 


6.7.87 


17.8.87 


21.9.87 


5.10.87 


6.10.87 


6.10.87 


1.12.87 


10.12.87 


22.12.87 


31.12.87 


31.12.87 


17.2.88 


6.3.88 


10.3.88 


1.10.S8 


6 


12 


12 


12 


12 


4 


6 


6 


7 


6 


6 


8 


3 


6 


3 


3 


3 


6 


50-2 


504 


52-0 


519 


56-0 


55-0 


54 1 


541 


541 


48-6 


47 9 


45-3 


46-3 


44 5 


43-7 


42-5 


427 


53-4 


+2-0 


+4-8 


+ 61 


+ 7-6 


+ 2-1 


-02 


+0-6 


+0-2 


+ 0-4 


-1-2 


-01 


-11 


-0-7 


-01 


o-o 


-0-5 


-01 


-1-5 


D-P 


S-P 


S-P 


D 


S-P 


R 


D-P 


D 


D-P 


S-P 


D-P 


D 


S 


R 


D-P 


S 


R-S 


P-S 


24 


25 


27 


23 


23 


22 


26 


25 


30 


26 


22 


21 


20 


21 


19 


20 


20 


34 



D, Davaar. P, Pladda. S, Sanda. R, Rhuad Point. 
* Mean of thirteen accordant soundings. t Observations made by F. C. " Vigilant." 

t The sign - in this line signifies that the point of observation was between the two stations denoted. 

Additional observations were made too near shore to be of equal value with the rest 
ob November 23rd, 1887, in 14 fathoms, when the mean vertical temperature was 
49°'6, and on February 1st, 1888, when the mean was 44°*1. 

The mean rate of change of temperature as deduced from observations on the western side 
of the Plateau was so unsatisfactory that it is unnecessary to enter into the details. It is 
sufficient to point out that differences of several degrees in mean temperature occurred in 
a distance of 4 or 5 miles, according to the position of the observing stations on the sea- 
ward or inner slope of the Plateau, and that such observations must obviously be much 
affected by local tidal conditions. This state of matters makes it impossible to estimate 
mean rates of change of temperature over any length of time, although for short periods 
when the temperature of the whole Area is fairly uniform a comparison might be safely 
attempted. 

The Plateau is so obviously a transitional zone between the oceanic and landward 
waters that it must be viewed in connection with both, and it can scarcely be treated as 
a separate natural region. 

General Form of Temperature Curve. — The fifty -two temperature curves for the 
Plateau, summarised in Tables VII. and IX., show an average slope, i.e., range of tempera- 
ture between the mean for the surface and bottom 5 fathoms, disregarding the sign, of 1°2. 
The curves resemble those of the Channel by having less than 0°'3 difference between 
top and bottom layers in February, March, September, and October, and occasionally in 



40 DR HUGH ROBERT MILL ON THE 

November and December. Stating this generally, we may say that the water of the 
Plateau is homothermic only just before the Spring minimum and just after the Autumn 
maximum. During the months of heating (from April to August) the surface water is 
usually more than two degrees warmer than the bottom layer, and may be as much as 
8 degrees warmer. This is the most heterothermic condition assumed by the water. The 
great warmth of the surface layers and its sharp contrast with that below may be 
accounted for mainly from the seaward extension of the hot surface water of the Arran 
Basin overlying the cooler water of the Channel. From the comparison of curves, it 
seems that the deeper layers on the seaward side of the Plateau usually correspond in 
temperature with the mass of water in the Channel. On the inner side, the Channel water 
of the deep layers of the Plateau is distinctly chilled by contact with the colder deep 
layers of the Arran Basin. 

Curves of negative slope occur from September to April, or during the season of cool- 
ing, when the surface water is colder than that beneath. It is interesting to notice that 
the negative slope on the Plateau was never so great as 2° in 25 fathoms, while the posi- 
tive slope at times amounted to close on 8°. 

Fig. 7, Plate XXIIL, shows the typical curves of the four seasons — those of warming, 
cooling, maximum, and minimum — on the Plateau. It will be noticed that the negative- 
slope curve of cooling is much less pronounced than the positive-slope curve of heating. 
It is natural to suppose that this may, to some extent, be due to the fact that all the 
winter observations were made during the day when cooling by radiation is at a 
minimum, while the summer observations, also made during the day, were at a time 
when solar radiation was at a maximum. It will presently be shown, however, that 
the positive form of the Summer curve is scarcely, if at all, modified during the night. 
We may assume also that the short and infrequent sunshine of winter does little to 
check loss of heat by surface radiation. The slighter slope of the negative curve is 
more probably explained by the fact that the water on the Plateau is practically of 
uniform salinity throughout, so that when the surface water is cooled its density is 
increased, and it sinks, rapidly chilling the mass by convection, and so tending to produce 
a homothermic state. The heated surface water, on the other hand, expands, and its 
density diminishes by rise of temperature more than it increases by the rise in salinity 
caused by evaporation. Hence the warm layer lingers on the surface, and the heat 
passes downward slowly. 

It is noteworthy that on the Plateau smooth curves are practically never obtained. 
At first sight, one would be inclined to attribute at least the minor irregularities to 
observational error, but experience and repeated experiments have convinced me that 
this is very rarely the case. A few of the more remarkable contorted Plateau curves are 
reproduced in fig. 8, Plate XXIIL, in order to illustrate the manner in which they vary. 
Nos. 14 (a), 2 (b), and 5 (c) show increasing degrees of complexity, due to the existence of 
layers of water superimposed at different temperatures, an effect possibly brought about by 
the complicated currents of the region, although, as will be shown immediately, instances of 



CLYDE SEA AREA. 41 

an intermediate maximum or minimum' occur for a much longer space of time than can 
be accounted for on the hypothesis of the tidal currents producing the irregular mixture. 
In the case of c, the minimum temperature at 13 fathoms is 52° "2, almost the same 
as that of the homothermic water of the Channel at the same time. The observation was 
made at a point nearly midway between Pladda and Sanda, but close to Sanda the 
curve (Table IX. No. 6) appeared homothermic at 52°*8. The sharpness of the included 
minimum between 9 and 14 fathoms in c leaves some room for the speculation that 
in the space between 5 and 15 fathoms in No. 6 (d) a similar minimum may have escaped 
attention. At anyrate, this justifies the great caution adopted in connecting the points 
of observation to form curves (see p. 9). The last example, Table VII. No. 6, of 
the Eastern division of the Plateau, fig. 8, e, is too wild in its zigzags to be 
accepted as natural, and it is only introduced to illustrate the necessity for keeping 
the vessel exactly in the desired position while all the soundings of a serial set are 
carried out. On this occasion the first sounding was made about 1^ miles to the 
south of Pladda, in a depth of 26 fathoms, and temperatures taken at 24, 14, and 4 
fathoms. The second sounding gave observations at 18, 8, and 3 fathoms, and the other 
points were then filled in. At the end, the extraordinary sequence of temperatures 
induced me to take another bottom temperature, when it appeared that the depth 
was only 18 fathoms, and the temperature at 17 fathoms 56°"2, and that the "Medusa" 
had been drifting toward the land while the observation was being: made, and so comins; 
into the much warmer shore water. The sea was rough, and the weather dull and rainy, 
so that landmarks could not be distinguished. The total drift was probably not more 
than quarter of a mile. 

Hourly Observations on Plateau. — On June 17th, 1887, a series of thirteen hourly 
observations was made when anchored nearly midway between Sanda and Pladda, 
Davaar bearing N.W. by N. f N. distant 6|- nautical miles. Observations were 
commenced at 20 h 0, and carried on until eight on the morning of the 18th. The depth 
varied from 26 to 27 fathoms, but the deepest water did not correspond with the 
theoretical hour of full tide, which was 21 h 30, low water occurring at 3 h 0. The tempera- 
ture of the air was 60° at the time of commencing observations, 59° at midnight, and 
58° at 2 o'clock in the morning. The thermometer for air- temperature was broken 
during the observations, but the air was not perceptibly colder after two o'clock. The 
night was dead calm, with a thick haze shutting out the stars and lighthouses, and 
thus tending to minimise the cooling due to radiation. 

The changes which occurred in the twelve hours were of a remarkable character. 
Fig. 9, Plate XXIV., shows the variation of temperature as ascertained hourly at the sur- 
face, 5 fathoms, 10 fathoms, 15 fathoms, and the bottom. The variation of the mean 
temperature of the whole slice of water is also shown, and the tidal phase is indicated 
below the figure. The surface temperature fell gradually but irregularly from 59°0 at 
20 h to 57° *3 at 8 h 0. A minimum occurred at 23 h 0, another very slight one at 3 h 
(57°'4), and a much deeper minimum (56 o> 0) at 7 o'clock on the 18th. At 5 fathoms 

VOL. XXXVIII. PART I. (no. 1). F 



42 DR HUGH ROBERT MILL ON THE 



there was a gentle rise from 51 0, 4 at 20 h to 52°'5 at l h during ebb tide, and 
then a gentle but fairly uniform fall with the rising tide to 51°*4 at 8 h 0. At 10 
fathoms the changes were more pronounced than elsewhere. Starting at 49° - 2 the 
water grew warmer somewhat irregularly until 2 h 0, when it was 51°'2. The next 
sounding, at 3 h 0, when it was low tide, was 48°*2, a drop of 3°, and the subsequent 
observations showed only a slight warming up to 48° "4 At 15 fathoms the temperature 
fell from 49°'5 at 20 h to 48°'2 at 23 h ; then rose to 49°"2 at 4 h 0, and remained constant 
at that temperature for the rest of the time. The bottom temperature was steady 
throughout at 49° "2, the greatest variation being one-tenth of a degree. 

The average temperature of the whole section was 50°'4 at 20 h 0, gradually rose to 
50 o, 7 at 3 h 0, and fell rather more rapidly to 49°*9 at 6 h 0, showing a tendency to increase 
again later. The sudden dive of the 10-fathom curve happened while the mean curve was 
stationary, thus showing that the cooling at 10 fathoms was not due to the intrusion of a 
mass of cold water. (The actual observations were made a few minutes after each hour). 

The interpretation of the mean curve evidently is that as the tide was ebbing the 
warmer surface water of the Arran Basin was tending to deepen on the Plateau, thus 
slightly raising the temperature as a whole, but on the flood tide setting in the cooler 
water of the Channel began to mix with the Plateau water. An attentive study of the 
vertical curves (fig. 10, Plate XXIV.), explains how the singular fall of temperature at 10 
fathoms occurred while the water as a whole remained unchanged in temperature. The 
mean value of the curves is given in No. 19, Table IX., where the mean slope is seen to 
be + 4°*8, the mean temperature of the surface 5 fathoms being 54 c, (extremes 55°*3 
and 52°"9), while the mean of the bottom 5 fathoms was 49°'2 (extremes 49°'3 and 49°'l). 
The first two soundings showed curves of a very simple type (a in fig. 10), where the 
temperature fell in a paraboloid curve to 1 5 fathoms, and below that became apparently 
homothermic. This simplicity entirely misled us, and, in spite of former experience, it 
was, unfortunately, not thought necessary to fix more points in the lower 10 fathoms. 
In all the subsequent soundings, however, this was done, and a remarkable distribution 
came into sight. The minimum was not at the bottom at all, but in a sharp elbow of 
the sickle-shaped curve, which at 23 h was found at 15 fathoms, with the value 48°'2 
(b in fig. 10). This very abrupt inversion was a constant feature of the curve, and on 
each successive sounding, the point at which it occurred was found to be higher up, and 
the inflexion became more pronounced. It reached 10 fathoms at 3 h 0, and so produced 
the sudden fall of temperature at that depth (c in fig. 10). There existed, in fact, 
a thin layer of cold water between the warm heterothermic upper mass of water and the 
cool homothermic lower layer. 

To show more clearly the changes in the distribution of temperature during the 
period, a time-depth diagram was constructed. This is shown in Plate II. fig. 2. 
In interpreting such a diagram it is necessary to remember that, when hours only are con- 
sidered, water in any considerable masses cools or heats so slowly that little rearrangement 
of the isotherms results from this cause. The isothermal sheets, traversino; a heterothermic 



CLYDE SEA AREA. 43 

mass of water, may thus be considered, if they be sufficiently numerous and the time suffi- 
ciently short, as limiting strata of water ; and any marked rearrangement of the isotherms 
must be looked upon as due to the effect of the mixture of contiguous strata, or the intrusion 
or withdrawal of some of them. In a time-depth section the heating of water from 
above by absorption of heat or affusion of warmer water on the surface is shown by the 
isotherms striking deeper. Cooling from the surface by radiation or by the withdrawal 
of warm upper layers, and the welling up of colder water from beneath, is indicated by a 
rise of isotherms toward the surface. The spreading out of isotherms apart from each 
other indicates a mixture of contiguous layers : the crowding together of isotherms may 
be due to the introduction above or below of water, differing greatly in temperature, or 
to a shearing motion squeezing the layers between successive isothermal sheets into 
less space vertically. 

In the diagram of Plateau observations it will be seen that until 1 o'clock in the 
morning all the isotherms had a downward trend, showing that heating was occurring 
from above. Now, no heat was reaching the water from the sun, which set within half 
an hour of commencing the observations. Nor was there a warm wind blowing, nor 
was the temperature of the air much above that of the surface water. Moreover, 
the maximum surface temperature occurred at midnight. It is perfectly obvious, then, 
that the heating must be due to warm surface water flowing to the position of observa- 
tion, and the ebb-tide carrying a strong current of warm surface water from the Arran 
Basin explains the effect fully. This surface water was accumulating on the Plateau, 
and displacing the homothermic layer of water derived from the Channel. The thin 
slice of water colder than 48°"5 served as a complete proof of the truth of this theory. 
At the time of observation (or, at least, a few hours previously), the mass of water 
in the Channel south of Sanda showed a minimum temperature of 48 0, 2 at 20 fathoms, 
and a temperature of 48°"7 on the bottom. Former experience indicates that the 
water further west, toward the Mull of Cantyre, would be homothermic and warmer ; 
probably — as indicated in the curve for mean temperature of the Channel — a little 
over 49°. This warmer water would possibly pass through Sanda Sound, and so cover 
the western part of the Plateau. But it is evident that a cold layer scarcely above 
48° separated the warmer bottom water from the relatively hot surface layers, and 
this is accounted for by the overflow from the West Arran Basin, which, although very 
warm on the surface, was colder than 48° at the level of the edge of the Plateau. 
The isotherm of 52° reached its greatest depth (5 fathoms) at 3 h 0, the lower isotherms 
at 2 h 0, but the isotherm of 49° below the cold layer at l h 0. It was low-water at 
3 o'clock, and then the sudden elevation of the cold layer from a mean depth of 1 5 fathoms 
to a mean depth of 10 fathoms took place, and the upper isotherms commenced to 
retreat toward the surface, while the mean temperature of the mass fell steadily, 
though slightly. The great thickening of the lower homothermic stratum, and the 
practically unaltered thickness of the cold layer above it, showed that the rising tide 
was carrying in Channel water beneath, and apparently raising up and causing to flow 



44 DR HUGH ROBERT MILL ON THE 

back the warm upper layers, the isotherms of which were greatly crowded just above 
the cold layer. 

Additional observations now suggest themselves which might have been made to 
throw light on many points still left doubtful, but enough has been made out, I think, 
to show that the flood-tide across the Plateau tends to carry in a mass of Channel 
water along the bottom, while the ebb-tide rather affects the surface. Probably there 
is always a current both in flood and ebb sweeping across the Plateau from surface to 
bottom, but during ebb the surface current seems to do most of the work, and in flood 
the under current. It is significant of this that the lowest isotherm in the diagram 
is the first to show an inflection due to the setting in of the flood stream, and the 
isotherms near the surface are the last. 

On the eastern side of the Plateau, as might be expected from its greater distance 
from the Atlantic, the range between surface and bottom temperature is greater than 
on the western side, but on the eio'ht occasions when observations were made on the 
same or on successive days, on both sides of the Plateau, the mean temperature of the 
vertical soundings never differed more than half a degree. 



The Arran Basin. 

This is the largest of the divisions of the Clyde Sea Area, and presents a peculiar 
importance in being the intermediary in all interchange of water between the ocean 
and the landward divisions. Water from the ocean, thoroughly mixed through all its 
depth in the Channel, and passed inward across the Great Plateau, finds in the Arran 
Basin a great reservoir in which it is mixed with landward water from rivers, estuary, 
and lochs, and from which it passes, carrying the influence of the open sea into the 
remotest recesses. The large island of Arran serves to divide the basin into three 
parts, the peculiarities of which are clearly marked. The West Arran Basin is practi- 
cally Kilbrannan Sound, and in its configuration resembles a sea-loch open at both ends. 
On the south the opening to the ocean across the Plateau resembles the opening of a 
sea-loch of the type of Loch Strivan. But the north or upper end sinks into the much 
deeper trough of the Central Arran Basin, so that the fjord-like character is confined 
to the steeply sloping parallel sides, and the gradually diminishing width from south 
to north. 

The East Arran Basin, on the contrary, is broad and open on the south, meeting 
the full breadth of the Plateau between Pladda and Turnberry Point. The trough 
of water deeper than 50 fathoms runs parallel to the east coast of Arran, and keeps 
close to the island, while on the east, a wide shallow, an extension northward of the 
Plateau, sweeps round the shore of the mainland. The relatively shallow portion may 
be said to occupy nearly two-thirds of the area of the eastern branch. The short 
north-eastern branch running between Bute and the Cumbraes contains a deep narrow 
basin barred off from the main trough, but of special interest, because in it the most 



CLYDE SEA AREA. 45 

complete series of regularly-spaced observations of temperature has been taken. 
Through this and the narrow, shallow Largs Channel on the east of the Cumbraes, 
the Arran Basin communicates with the Dunoon Basin. 

The Central Branch runs from the north of Arran, throwing off a shallow branch into 
the Kyles of Bute, practically due north to Otter Ferry, where it communicates directly 
with Loch Fyne. It is the deepest part of the Arran Basin, and the bottom is very 
irregular. At the head it shoals up rapidly, stopping in the very shallow Loch Gilp, and 
Loch Fyne joins it across a sharply defined bar of no great depth. 

Although the three main branches of the Basin have individual peculiarities which 
subject the water contained in them to special conditions, the Arran Basin is essentially 
one. The orographical map (Plate 2 part I.) shows that the water over 50 fathoms in 
depth in the three branches is continuous, the main trough running almost S.S.E. from off 
Kilfinan to off Largybeg, and about the middle, off Inchmarnoch, sending a branch down 
Kilbrannan Sound as far as Carradale. The main trough of over 80 fathoms runs straight 
across the mouth of Kilbrannan Sound, from off Tarbert to off Corrie. 

The relatively small number of stations at which observations were made in this 
great division makes it necessary to treat it somewhat generally. Accordingly, the record 
of each station will first be considered briefly, and then the conditions of the deep part of 
the Basin will be discussed as a whole. 

Only a few irregular observations were made in the southern part of the West Arran 
Basin, and the results of them are referred to when describing the general temperature 
sections. ' 

Observations off Carradale. — The deepest part of Kilbrannan Sound, between 
Imachar and Carradale, is extremely irregular in its configuration, and the station was not 
always exactly the same. Water of depths sometimes exceeding 80 fathoms occurs close to 
shallows of 20 fathoms or less. The observations are all, however, characteristic of the 
deepest part of the West Arran Basin. 



[Table 



46 



DR HUGH ROBERT MILL ON THE 
Table X. — Temperature Observations off Carradale. 



No. . . 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


lit 


12 


Date . . 


20.9.78 


25.8.85 


19.6.86 


13.8.86 


26.9.86 


18.11.86 


24.12.86 


11.2.87 


30.3.87 


9.5.87 


12.5.87 


18.6.87 


No. of Pts. 


13 


7 


9 


13 


10 


12 


9 


6 


9 


6 


10 


15 


Temp. . . 


52-9 


50-8 


45-1 


48-5 


50-9 


51-0 


47-5 


43-6 


43-8 


44-9 


45-2 


47-8 


Slope . . 


+ 4-1 


+ 5-8 


+ 5-0 


+ 6-2 


+ 4-4 


-2-0 


-1-0 


-0-9 


o-o 


+ 2-5 


+ 1-6 


+ 6-9 


H.D. . . 





30 


40 


20 


30 


25 


50 


60 


75 


45 




25 


Ji.t. . . . 




49-3 


44-0 


47-0 


49-2 


51-5 


47-7 


43-7 


43-8 


44-2 




46-2 


No. . . 


13 


14 


15 


16 f 


17 


18 


19 


20 


21 


22 


23 




Date . . 


7.7.87 


17.8.87 


22.9.87 


3.11.87 


5.12.87 


9.12.87 


23.12.87 


28.12.87 


30.1.88 


15.2.88 


22.3.88 




No. of Pts. 


12 


12 


9 


13 


16 


15 


9 


15 


9 


12 


12 




Temp. . 


48-7 


51-0 


52-7 


51-2 


48-8 


47-9 


46-0 


45-9 


44-8 


44-4 


42-5 




Slope . . 


+ 8-1 


+ 8-4 


+ 3-8 


-2-1 


-0-2 


-0-3 


-1-3 


-1-8 


-0-2 


-0-8 


-1-0 




H.D. . . 


40 


40 


30 


30 


80 


80 




60 


80 


40* 


35 




h.t. . . . 


47-1 


48-9 


51-6 


52-1 


48-8 


47-9 




46-1 


44-8 


44-2 


42-8 





Assume 80 fathoms as depth. 
* Here the homo-thermic 40 fathoms were the upper half, f Observations made by F.C. " Vigilant.'' 

In Table X. two data are tabulated which acquire much importance in the Arran 
Basin. These are the homothermic depth (H.D.), i.e. the depth of the mass of water in 
which the whole range of temperature is less than 0°*5. This is almost always the lower 
part of the water, and in order to arrive at comparable results the depth is assumed as 
80 fathoms in all cases (although occasionally the sounding may have been in slightly 
shallower, and sometimes in slightly deeper, water), and the homothermic depth is arrived 
at by subtracting from 80 the depth in fathoms at which the homothermic part begins. 
The second datum, h.t., is the mean temperature of the homothermic layer. Incidentally, 
this is, of course, the mean temperature of the lowest five fathoms, so that by adding 
(algebraically) the slope, the mean temperature of the upper five fathoms is at once 
obtained. 

Observations 1 and 2 of Table X. were made by Mr J. Y. Buchanan, F.R.S., in 1878 
and 1885 respectively; Nos. 11 and 16 were done on the Fishery cruiser "Vigilant" 
in 1887 ; the remainder were all done on the "Medusa." 

The curves were practically homothermic in the cold months, December to March. 
During the period of heating, May to August, the positive slope of the curves greatly 
increased, the homothermic layer shrunk until it occupied the lower third only, and the 
form of the curve was practically a paraboloid, although occasionally very irregular in 
outline. The upper part of the curve then assumed a negative slope, and the water 
rapidly became homothermic as the minimum approached. 



CLYDE SEA AREA. 



47 



It is an interesting fact that the homothermic mass of water covering the bottom 
changed its temperature as rapidly as did the whole quantity of water, surface included, 
and often more rapidly. There is no trace of these heat transactions taking place through 
the upper layers, and the evidence points clearly to an equalisation of temperature 
beneath by under currents, while the upper layers, if mixed at all, were so much influenced 
by radiation or surface drainage from the land that equilibrium was rarely established. 

As all the stations of the Arran Basin showed the same order of phenomena, the 
complete discussion of Garroch Head and Skate Island, where the observations were most 
numerous, will suffice to illustrate the seasonal changes for the whole. 

Observations off Loch Ranza. — Observations were made at the head of Kilbrannan 
Sound, about midway between the Island of Arran and Skipness Point, with Loch Ranza 
open. This was in the deep channel of the West Arran Basin, before it united with the 
West and Central Arran Basin off Inchmarnoch. 

Table XI. — Temperature Observations off Loch Ranza. 



No. . . . 

Date . . . 
No. of Points 

Temp. . . 

Slope . . . 

H.D.*. . . 

h.t. . . . 



1 

9.2.87 

6 

44 

-0-6 

45 

44-0 



2 

30.3.87 

6 

43-8 

-0-2 



3 
9.5.87 

6 

46-0 

+2-3 



4 
18.6.87 

6 

50-1 

+6-4 



5 

7.7.87 

9 
48-6 
+ 8-5 

10 
46-3 



6 

22.9.87 

6 

53-1 

+3-6 





7 

5.12.87 

12 

48-3 

-0-3 



2.1.88 

9 
459 
-1-4 

35 
46-2 



9 
15.2.88 

9 
44-5 
-0-9 

30 
44-7 



Only mentioned when sounding is 50 fathoms or over, and taken with reference to depth of 55 fathoms. 



The observations at this station were less satisfactory than at most of the others. In 
the main they corresponded closely with those at Carradale. 

Observations off Largybeg. — Observations were made in the deep trough lying about 
two miles east of Arran, with Largybeg Point abeam. This is near the southern end of 
the great depression of the East Arran Basin, where it begins to shoal toward the 
Plateau. 

Table XII. — Temperature Observations off Largybeg. 



No 

Date . . . 
No. of Points 
Temp. . . . 
Slope . . . 
H.D. . . . 
h.t 



1 

9.7.84 

4 

50-0 

+9-6 

20 

47-9 



3 

12.8.86 9.2.87 
13 



49-6 

+77 




43-4 
-0-3 



4 

5.5.87 
9 

44-8 
+4-4 



5 
17.6.87 

15 
47-8 
-(-6-1 

30 
46-1 



6 

12.8.87 
11 
52-8 

+7-6 




20.9.87 

7 

53-3 

+2-5 



8t 
5.10.87 
11 
53-9 
+ 0-6 
30 
53-5 



9t 

10.10.87 

10 

54-2 

+2-5 

30 

53-1 



10 
10.12.87 

9 

48-0 
-0-2 

60 
48-0 



lit 
13.1.85 
14 
45-6 
-1-3 
30J 
45-8 



12 13 

17.2.88 30.3.88 
9 



43-5 
-1-5 
30* 
43-0 



41-9 

-0-5 

60 

41-9 



14 

8.4.8? 

9 

42-3 

+ 0-7 

50 

42-1 



15+ 

19.10.88 
8 

517 

-0-4 

30 

51-9 



16 
18.12.8; 

8 
46-5 
-1-9 





Depths assumed, 60 fathoms. Depths over 45 alone considered. 
1 The Upper 30 Fathoms homothermic. + Observations by "Vigilant." J Compare with 12.1.88 when=60 and 45"3. 



48 



DR HUGH ROBERT MILL ON THE 



The curves are roughly similar to those of Carradale, so much so that in February 1888 
both stations showed the upper 30 fathoms of water in a homothermic condition. 
Frequently in summer the mean temperature at Largybeg, and also the positive slope, 
w r ere somewhat greater than at Carradale. The curves, too, showed more variety. In 
August the whole mass of water became heterothermic, with a strong positive slope. 
On both occasions (Nos. 2 and 6) these curves approximated more to the North 
Atlantic type than any others observed in the Sea Area. They are reproduced as a and 
b in fig. 11, Plate XXIV. An approach to a sickle-shaped curve, c, is also shown. The 
peculiarities of these curves may be due to the great surface of shallow water to the 
eastward, which in summer acquires a high temperature. 

Observations off Brodick. — The position in which observations were made at this 
station should have been the greatest depth of the West Arran Basin, lying about 5% 
miles east of the coast of Arran, with Brodick Bay open ; but on account of the frequent 
roughness of the sea and the absence of convenient landmarks, the exact position was 
not always found. 



Table XIII. — Temperature Observations off Brodick. 



No. . . 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 


14f 


15 


16 


17 


18 


19f 


Date . . 


13.6.79 


15.4.86 


17.4.86 


20.6.86 


23.9.86 


19.11.86 


26.12.86 


9.2.87 


3.4.87 


5.5.87 


17.6.87 


12.8.87 


20.9.87 


27.10.87 


10.12.87 


17.2.88 


30.3.88 


19.8.88 


19.12.88 


No.ofPts. 


10 


6 


8 


5 


4 


9 


9 


6 


10 


13 


18 


15 


9 


13 


12 


12 


9 


6 


8 


Temp. . 


43-9 


41-6 


41-5 


45-4 


52-4 


50-8 


47-4 


43-7 


43 6 


44-6 


47-7 


50-1 


52-0 


52-5 


47-6 


44-4 


42-0 


50-6 


46-8 


Slope . 


+ 9-4 


+ 1-2 


+ 1-4 


+ 6-7 


+ 4-5 


-1:3 


-2-2 


-0-8 


+0-6 


+3-3 


+ 6-4 


+ 8-9 


+ 5-6 


-0-9 


-2-1 


-1-9 


-0-5 


+7-5 


-1-4 


H.D. . 


55 


70 


65 


45 





50 


35 


45 


30 


50 


50 


10 





40 


45* 


40 


30 


10 


35 


h.t. . . 


427 


41-5 


41-4 


44-1 




51-2 


48-0 


44-2 


42-8 


44-3 


46-3 


47-1 




52-9 


47-6 


44-8 


42-4 1 47-1 


47-4 



Assume depth as 75 fathoms. 
Below the homothermic layer comes 15 fathoms of rapid slope. 



+ Observations by F.C. "Vigilant. 



The curves on the whole closely resembled those observed at the same date at the 
Largybeg station. As in the former instance, there were several curves closely 
approaching the oceanic type, and in particular two remarkable specimens of inverted 
positive curves were presented in September 1886 and September 1887, Nos. 5 and 13 
in Table XIII. These were the only cases in which there was no homothermic water 
present, but the variation in the depth of the homothermic water at other seasons was 
somewhat irregular. 

Cross- sections in East Arran Basin. — In August 1886 and September 1887 a 
number of observations were made in order to test the influence of the shallow shore 
waters on the general temperature of the whole about the time of the annual 
maximum. 

On August 27th, 1886, observations were made at several points between Whiting Bay, 
in Arran, and Ayr, a distance of 17t> miles. The surface temperature on the Arran coast 
was 55°"3, in mid-channel 55 9 '4, and on the Ayrshire coast 57°'5. On a section drawn to 



CLYDE SEA AREA. 49 

represent the distribution of temperature in depth, the isotherms ran nearly straight from 
the Arran coast across the deep water until the depth diminished to 25 fathoms on the 
coast of Ayr ; the temperature at 15 fathoms being 53 o, 0, and at 25 lathoms 51 o, 0. But 
at this line, about 3 miles from the shore, the isotherms suddenly dipped, 55° being the 
bottom temperature when the depth became 15 fathoms. This indicates the accumula- 
tion of a belt of warm water along the gently sloping shore to a distance of three miles. 
The strip of water, from the land down to the depth of 15 fathoms, had an average 
temperature about 56°, while the average of the surface stratum 15 fathoms thick, across 
the Basin to the edge of the warm water, was about 54°. The weather during this trip 
was fine, with a light south wind blowing at right angles to the plane of the section, and 
a slightly ruffled sea. 

On September 20th, 1887, two cross-sections were made in perfectly calm weather, the 
day being very warm, with slight haze. The first series of observations, from the 
depression between Garroch Head and Cumbrae Light to Brodick, showed the lower 
isotherms running horizontally. That of 52° coincided with the depth of 40 fathoms ; 
water below this temperature was confined to the deep part of the East Arran Basin, and 
did not cross the ridge into the depression of the north-east branch. The isotherm of 
53° was horizontal at 30 fathoms until within 2 miles of the Garroch Head sounding, 
when it dipped suddenly. The isotherms of 54° and 55° were curved. The former 
was at 30 fathoms off Garroch Head, rose to 15 fathoms in the deepest part of the trough, 
and sank to 21 fathoms against the Arran coast. The isotherm of 55° rose from 
1 5 fathoms, 2 miles from Garroch Head, to the surface at the deepest sounding, and sank 
to 1 8 fathoms against the Arran coast. This showed that the upper layers of the deepest 
water were on the average, at the same plane, nearly a degree colder than the water along 
the coast. 

A more important section was then made from Brodick Bay to Irvine, a distance of 18^ 
miles. The section drawn from the observations is given in fig. 12, Plate XXIV. The 
of surface temperature was practically constant at 56° all the way over, and until the depth 
45 fathoms was reached, beyond the deepest trough, the other isotherms ran in the main 
horizontally, 55° at about 15 fathoms, 54° at about 23, and 53° at about 30 fathoms. 
But when the depth of 30 fathoms was reached, 2^ miles further, and 4^ miles from the 
Ayrshire coast, the bottom temperature was over 55°, so that the isotherms must have 
dipped very abruptly. On this occasion the upper layer of 30 fathoms had an average 
temperature of about 54°'7 all the way from the Arran coast for 11| miles, until the 
depth of 45 fathoms on the Ayrshire coast was reached, where it met a body of shallow 
water 7 miles wide, averaging 55° - 6 in temperature. Here there was a smaller actual 
difference of temperature between the deep and the shallow water than in August 1886, 
but a very much larger quantity of water had been affected by the heating power of the 
shallows. 

Since so few observations were taken along the wide shallow coast of Ayr, it is 
obviously impossible from the data collected to estimate the total heat content of the 

VOL. XXXVIII. PART I. (NO. 1). G 



50 DR HUGH ROBERT MILL ON THE 

Arran Basin at a given time with any approach to accuracy. All we can say definitely, 
from the two cross-sections available, is that in summer the isothermal sheets are flexed 
upward in the deepest water, and downward toward the shore, the abruptness of the 
downward bend being in some inverse proportion to the gradient of the shore. 
Were it not for the section (fig. 12) being made in a spell of anticyclonic calm, 
the influence of a west wind might have been credited with producing the isothermal 
arrangement shown. 

From observations I made previously on a wide sand-beach on the Firth of Forth, it 
appears that in winter the water resting on the beach is chilled, relatively to that beyond 
shore influence, in much the same proportion as it is heated by contact with the sand in 
the summer. What is true of a tidal beach probably holds for shallow water generally, 
and we may conclude that the isothermal sheets will be curved upward by shallow water in 
calm weather during winter, when the shore waters are colder than those in mid-channel. 

In discussing the distribution of temperature in a mass of water, it is important to 
consider isothermal sheets, which are never, except in rare circumstances, horizontal planes. 
Isothermal lines plotted on a section simply represent sections of the isothermal sheets, 
the convolutions of which, in some cases, are very complicated. An attempt might be 
made to construct a model, showing by thin sheets of coloured gelatine the arrangement 
of water-temperature in three dimensions, but it does not admit of easy diagrammatic 
representation on paper. 

Observations between Garroch Head and Cumbrae Light. — The tongue of deep 
water branching off from the East Arran Basin between Bute and Little Cumbrae 
is the main channel through which the seaward water reaches the Dunoon Basin, 
and through it the eastern lochs and estuary. Being close to Millport, the head- 
quarters of the " Medusa," it was found possible to make very frequent observations 
in a depth of 60 fathoms. 

The fifty-one observations made in this depression are very interesting, and might 
be discussed in great detail. As, however, it is more important in some ways to study 
minutely the effects of heat in the deeper water off Skate Island, I shall here treat only 
of the main features of the Garroch Head observations. 

In form the curves resembled those obtained off Brodick, but the larger number 
allows one to study the form of the curve in relation to season with some prospect of 
trustworthy results. 

Positive slope was shown in the vertical curve on twenty-two occasions, zero slope 
once, and negative slope twenty-eight times. The positive slope was always much 
greater than the negative ; thus on fifteen occasions the surface layer of 5 fathoms 
was more than 2°*3 warmer than the bottom layer of the same depth, while only once 
was it more than 2° '3 colder. The maximum positive slope was 9° 7, the maximum 
negative slope 3° "2. This shows in an interesting way how heated water keeps to the 
surface, while cooled water sinks and equalises the temperature, the salinity at surface 
and bottom not being very different at this station. 



CLYDE SEA AREA. 



51 



The rate of gain and loss of heat by the mass of water as a whole, and by the upper 
and lower layers, is given in Table XV., which shows the best results that our work on 
the Clyde Sea Area produced regarding temperature changes in comparatively short 
intervals of time. Sounding No. 25 is omitted from consideration, because it was made 
under different conditions, and possibly not quite in the same place as soundings 24 and 
26. The effect of the different behaviour of heated and chilled surface water is brought 
out by the much greater average rate of cooling than of heating. 



Table- XIV. — Temperature Observations off Garroch Head. 



No. . . 


1 


2 


3 


4 


5 


6 


7 


8 


8a 


9 


9a 


10 


11 


12 


13 


14 


i 15 


Date . . 


29.8.78 


21.9.78 


24.8.85 


17.4.86 


21.6.86 


6.8.86 


13.9.86 


29.9.86 


29.9.86 


13.11.86 


15.11.86 


2.12.86 


11.12.86 


16.12.86 


27.12.86 1.1.8710.1.87 


No.of Pts. 


13 


14 


7 


9 


5 


13 


7 


7 


7 


7 


8 


9 


11 


9 


12 


10 


11 


Temp. . 


51-0 


52-9 


50-2 


41-6 


45-3 


48-9 


517 


53-3 


53-2 


51-3 


51-2 


49-8 


48-3 


47-4 


45-8 


45-8 


45-1 


Slope . . 


+9-7 


+6-6 


+ 9-0 


+ 1-5 


+ 6-0 


+ 5-9 


+ 5-4 


-0-9 


-0-7 


-1-6 


-0-9 


-21 


-1-4 


-17 


-2-3 


-1-0 


-3-2 


H.D. . 











40 


40 


25 


10 


20 


25 


40 


50 





30 


40 


30 


35 


20 


h.t. . . 








41-4 


44-3 


47-5 


49-4 


53-6 


53-5 


51-6 


51-1 




48-6 


47-6 


46-3 


46-0 


46-0 


No. . . 


16 


17 


18 


19 


20 


21 


22 


23 


24 


25+ 


26 


27+ 


28 


29 


30 


31 


32 


Date . . 


20.1.87 


31.1.87 


12.2.87 


1.3.87 


8.3.87 


18.3.87 


3.4.87 


9.4.87 


19.4.87 


4.5.87 


5.5.87 


26.5.87 


16.6.87 


6.7.87 


1.8.87 


16.8.87 


20.9.87 


No.of Pts. 


8 


2 


9 


8 


8 


10 


8 


9 


8 


9 


10 


11 


12 


12 


12 


15 


9 


Temp. 


44-1 


44-1 


43-9 


43-7 


43-8 


43-7 


43 6 


43-9 


44-0 


44-4 


44-6 


45-6 


47-9 


48-7 


51-3 


52-2 


53-8 


Slope . . 


-0-8 


-0-2 


-1-9 


+ 0-2 


-0-5 


-0-8 


+ 0'2 


-0-2 


+ 1-0 


+ 2-3 


+2-4 


+2-5 


+ 7-1 


+2-9 


+ 8-9 


+ 4-9 


+ 1-8 


H.D. . 


20 


60 


50 


50 


55 


45 


50 


60 


50 


25 


40 


15 


10 


50 


20 


30 


20 


h.t. . . 


44-0 


44-1 


44-1 


437 


43-8 


43-9 


43-5 


43-9 


43-9 


43-1 


44-3 


44-0 


46-4 


48-3 


48-0 


51-0 


53-2 


No. . . 


33f 


34f 


35 


36 


37 


38 


39 


40f 


41+ 


42 


43 


44 


45 


46+ 


47 


48 


49 


Date . . 


25.10.8; 


31.10.87 


10.11.87 


2.12.87 


15.12.87 


19.12.87 


8.1.88 


13.1.88 


16.1.88 


11.2.88 


17.2.J 


830.3.8 


8 10. 4. 8 i 


11.5.88 


16.5.88 


29.8.88 


29.10.88 


No. of Pts. 


9 


10 


11 


9 


9 


15 


9 


9 


8 


9 


12 


9 


9 


9 


12 


8 


6 


Temp. . 


52-3 


52-1 


50-6 


4S-4 


46-6 


46-2 


45-5 


45-1 


45-4 


44-3 


44-4 


42-1 


42-4 


43-9 


43 9 


51-1 


51-0 


Slope . . 


-1-1 


-1-3 


-2-1 


-0-2 


-1-6 


-2-1 


-0-1 


-0-7 


-1-4 


-0-3 


-1-3 


-0-4 


+ 1-3 


+ 3-0 


+3-3 


+ 5-9 


o-o 


H.D. . 


25 


50 





50 


20 


50 


30 


55 


35 


50 


10 


60 


40 


35 


30 


10 


60 


h.t. . . 


52-6 


52-1 




48-4 


47-4 


46-4 


45-5 


45'2 


457 


44-3 


44'E 


42-1 


42-2 


43-1 


43-2 


48-8 


51-0 



+ Observations by F.C. "Vigilant." 



52 



DR HUGH ROBERT MILL ON THE 



Table XV. — Rate of Change of T em/per atxire off Garroch Head. 







Section— 


Whole Depth. 


Upper 


5 Fathoms. 


Bottom 


5 Fathoms. 


Date. 


No. of 
Days. 














Temp. 


Temp. Change 


Temp. 


Temp. Change 


Temp. 


Temp. Change 




63 


Change. 


per Day. 


Change. 


per Day. 


Change. 


per Day. 


17Ap.86-21June 


+ 3-7 


+ 0.059 


+ 7-3 


+ o - n6 


+ 2-8 


+ 0-044 


21 June-6 Aug. . 


46 


+ 3-6 


+ 0*079 


+ 3-0 


+ 0-065 


+ 3-1 


+ 0-067 


6 Aug.-13 Sep. . 


38 


+ 2-8 


+ 0-074 


+ 1-6 


+ 0-042 


+ 2-1 


+ 0-055 


13 Sep.-29 Sep. . 


16 


+ 1-6 


+ o*ioo 


-1-8 


- O'lIO 


+ 3-5 


+ 0*219 


29 Sep.-15 Nov. 


47 


-2-1 


- 0.045 


-2-6 


-0-055 


-2-6 


-0-055 


15 Nov.-2 Dec. . 


17 


-1-4 


— 0*082 


-1-3 


— 0-079 


-0-3 


- 0-019 


2 Dec.-ll Dec. . 


9 


-1-5 


- 0.169 


-1-7 


-0-188 


- 2-2 


- 0-244 


11 Dec-16 Dec. . 


5 


-0-9 


- 0.180 


-1-5 


- 0-300 


-1-2 


-0-250 


16 Dec.-27Dec. . 


11 


-1-6 


-0.149 


-1-6 


-0-149 


-1-0 


- 0*091 


27Dc.86-Ua.87 


5 


o-o 





+ 0-7 


+ 0-140 


-0-6 


- 0'120 


1 Jan. -10 Jan. . 


9 


-0-7 


- 0*078 


-2-2 


- 0-244 


+ 0-2 


+ - 022 


10 Jan.-20 Jan. . 


10 


-1-0 


- 0*100 


+ 0-4 


+ 0-040 


-2-0 


— 0'200 


20 Jan.-31 Jan. . 


11 


o-o 


O'O 


+ 0-8 


+ 0-073 


+ 0-2 


+ 0-018 


31 Jan.-12 Feb. . 


12 


-0-2 


- 0*016 


-1-8 


-0-150 


-o-i 


- o - oo8 


12 Feb.-l Mar. . 


17 


-0-2 


— 0"0I2 


+ 1-7 


+ O'lOO 


-0-4 


- 0-023 


1 Mar. -8 Mar. . 


7 


+ 0-1 


+ 0*014 


+ 0-6 


+ 0-086 


+ 0-1 


+ 0*014 


8 Mar.-18 Mar. . 


10 


-o-i 


- 0*010 


-o-i 


- O'OIO 


+ 0-2 


+ 0'020 


18 Mar.-3 Ap. . 


16 


-0-1 


- 0*006 


+ 0-7 


+ 0-044 


-0-3 


— o'oiS 


3 Ap.-9 Ap. . . 


6 


+ 0-3 


+ 0*050 


-0-1 


- 0*017 


+ 0-3 


+ 0*050 


9 Ap.-19 Ap. . . 


10 


+ 0-1 


+ 0*010 


+ 1-2 


+ 0'I20 


o-o 


O'O 


19 Ap.-5 May . 


16 


+ 0-6 


+ 0-037 


+ 1-6 


+ o - ioo 


+ 0-2 


+ 0'OI2 


5 May-26 May . 


21 


+ 1-0 


+ 0-048 


+ 0-1 


+ 0-005 


o-o 


O'O 


26 May-16 June 


21 


+ 2-3 


+ o'no 


+ 6-8 


+ 0-324 


+ 2-2 


+ 0-109 


16 June-6 July . 


20 


+ 0-8 


+ 0-040 


+ 1-4 


+ 0-070 


+ 1-8 


+ 0*090 


6 July-1 Aug. 


26 


+ 2-6 


+ o'ioo 


+ 4-8 


+0-185 


-0-2 


- 0-009 


1 Aug. -16 Aug. . 


15 


+ 0-9 


+ 0*060 


-1-2 


— o - o8o 


+ 2-8 


+ 0-189 


16 Aug.-20 Sep. . 


35 


+ 1-6 


+ 0-046 


-0-9 


— 0-026 


+ 2-2 


+ 0-063 


20 Sep.-25 Oct. . 


35 


-1-5 


-0-043 


-3-2 


- 0-091 


-0-3 


- 0-009 


2-". Oct. -31 Oct. . 


6 


-0-2 


-0-033 


-0-6 


- O'lOO 


-0-4 


— 0*067 


31 Oct.-10 Nov. . 


10 


-1-5 


-0-150 


-1-7 


- 0*170 


-0-9 


- 0-090 


10 Nov.-2 Dec. . 


22 


- 2-2 


- 0*100 


-1-2 


-0-054 


-31 


- 0*141 


2 Dec-15 Dec. . 


13 


-1-8 


-0-138 


-2-3 


- 0-176 


-0-9 


- 0070 


15 Dec-19 Dec. 


4 


-0-4 


— o"ioo 


-1-5 


-°'375 


-1-0 


-0*250 


19 Dc. 87-8 Ja. 88 


19 


-0-7 


-0-037 


+ 1-3 


+ 0-069 


-0-7 


-0*037 


8 Jan.-13 Jan. . 


5 


-0-4 


- 0*080 


-1-1 


- - 220 


-0-5 


- o*ioo 


13 Jan.- 16 Jan. . 


3 


+ 0-3 


+ o-ioo 


-0-2 


- o"o66 


+ 0-5 


+ 0*166 


16 Jan.-ll Feb. . 


26 


-11 


— 0-042 


-0-4 


-0-015 


-1-3 


+ 0*050 


11 Feb.-l 7 Feb.. 


6 


+ 0-1 


4- o - oi6 


-0-7 


- 0-117 


+ 0-5 


+ 0*083 


17 Feb. -30 Mar.. 


41 


-2-3 


-0-056 


-1-3 


-0-031 


-2-6 


- °'°53 


30 Mar.-lO Ap. . 


11 


+ 0-3 


+ 0-026 


+ 1-6 


+ 0-145 


-o-i 


- 0*009 


10 Ap.-ll May . 


31 


+ 1-5 


4- 0-048 


+ 2-6 


+ 0-084 


+ 0-9 


+ 0*029 


11 May-16 May. 


5 


o-o 


O'O 


+ 0-2 


+ 0-040 


-o-i 


— 0*020 


16 May-29 Aug. 


105 


+ 7-2 


+ o - o68 


+ 8-4 


+ 0*080 


+ 5-8 


+ o"°55 


29 Aug. -29 Oct. . 


61 


-01 


- o - oi6 


-3-7 


- 0*060 


+ 2-2 


+ 0*036 



CLYDE SEA AREA. 



53 



The averages taken from Table XV., omitting the cases of no change of temperature, 
are shown in Table XVI. Koughly speaking, the fall of temperature is one-third more 
rapid than the rise. 

Table XVI. — Average Daily Rate of Heating and Cooling in F.° 





Whole Mass. 


Surface Layer. 


Bottom Layer. 


Heating. 


Cooling. 


Heating. 


Cooling. 


Heating. 


Cooling. 


Average rate, 
Maximum rate, . 
Number of cases, 


+ 0-057 

+ 0-110 

19 


- 0075 
-0-180 

22 


+ 0-096 

+ 0-324 

20 


-0-120 

-0-375 

24 


+ 0-069 
+ 0-219 

20 


-0-086 
-0-250 

22 



These averages are, of course, not strictly comparable, as they are not the averages of 
equal periods ; but they are quite trustworthy for the comparison of temperature changes 
at surface and bottom with those of the whole mass. The surface layer heated and cooled 
one-third more rapidly than the bottom layer, while, on account of intermediate changes, 
the whole mass of water changed its temperature more slowly than either of its extreme 
surfaces. The much more rapid progress of cooling than of heating, indicated by the 
greater positive than negative slope of the vertical curves, and demonstrated by the 
averages given in Table XVI., is probably entirely due to the aid which downward 
convection gives to the processes of heat transference by conduction, and mixture by 
winds or tidal currents. 

Homothermic conditions preponderated in the months of falling and minimum 
temperature, but were restricted to the lower layers, and sometimes lost altogether during 
the months of rapid heating and maximum temperature. Observations of density at 
Garroch Head were not made as often as was to be wished. The average of six at wide 
intervals gave the surface density at 60° as 1*02417 and the bottom 1 '02504. This gives 
for homothermic conditions a range of —0*00087, which for the greatest positive slope 
( + 9°*7) would be increased to -0*00226, and for the greatest negative slope (-3°*2) 
diminished to —0*00050, which might lead to a reversal of the density gradient very 
readily. The downward convection, which occurs at intervals during the months of 
cooling, naturally tends to perpetuate a homothermic state, and so make it characteristic 
of the season ; but even during the period of warming, the heterothermic condition, 
incidental to the gain of heat by surface exchange, may be overcome in a day or two by 
the influence of strong wind from a direction which ensures complete mixing of the water. 

Some sets of consecutive curves showing the phenomena of temperature changes may 
be cited as characteristic. 

Fig. 13, Plate XXIV., shows very well the transition from a marked positive to a slight 



54 DR HUGH ROBERT MILL ON THE 

negative slope at the period of maximum. The curve A has mean temperature 51°*7, and 
its form approaches the oceanic type, already showing equalisation of temperature in the 
upper layer. Curve B, sixteen days later, shows that the surface layer of 5 fathoms has 
cooled l° - 8 by radiation upward, and conduction downward, probably the latter predomi- 
nating. At 22^ fathoms the temperature is the same in both, but below that very great heat- 
ing has gone on, the rate of increase of temperature increasing with the depth, so that in 
the bottom 5 fathoms there was a rise of 3° '5 — twice as much as the loss at the surface. 
Curve B has mean temperature 5 3° "3, the highest temperature observed at this station 
with a negative slope. Unfortunately, the density of the water was not determined on 
either occasion. It might be supposed that, as the surface water cooled to a certain 
temperature between 55° and 53°, its density became greater than that beneath, and 
mixture resulting in equalisation of temperature immediately ensued. It is unlikely, 
however, that so decided an increase of density would result, but a decrease of density 
gradient would greatly facilitate the action of tide and wind in producing mixture. Figure 
14, Plate XXIV., is an interesting case of the steady fall of temperature in winter, 
the curves retaining a distinct negative slope. In A the surface cooling seems to have 
been prevented from producing its full effect more than half-way down ; but in B and 
C the curves show very regular cooling, the rate increasing towards the bottom. Curve 
D shows the remarkably superficial effect of very cold weather when the surface water 
is much fresher than that beneath, and curve E shows how the surface chilling was 
annulled a few days later, probably by warmer water brought from the seaward part of 
the Basin by the tide, while cooling went on steadily below. The mean temperature of 
curves D and E is, however, practically unchanged : the effect might be due to mixture 
only. 

Fig. 15, Plate XXV., illustrates with more detail than fig. 13 the gradual process by 
which the great slope of the curve of heating diminishes as the maximum temperature 
approaches, and how the fall of surface temperature goes on while the temperature of the 
mass as a whole, and of the bottom temperature especially, continues to rise. Al- 
though the volume of the water near the surface is much greater than that at greater 
depths, it is not likely that the cooling of the upper 17 fathoms by 2° can give out 
heat enough to warm the lower 40 fathoms by nearly 5°, and we must look elsewhere 
than to the surface for the main source of heat. This in the present case was probably 
the warm water filling the Dunoon Basin, which appeared to catch and store up the 
comparatively warm upper layers of the Arran Basin, and by a return underflow affected 
the Garroch Head depression. 

Fig. 16, Plate XXV., serves to show how gradually the homothermic curve resumes a 
positive slope as surface heating recommences in Spring. The lower 45 fathoms 
remain practically unchanged, while the surface layer has been warmed up by two 
degrees, and the slow penetration of the heat downward is shown by the typical 
paraboloid form of the upper part of the curve. 

Combining all the results shown above in figures and curves into a section illustrating 



CLYDE SEA AREA. 55 

the distribution of temperature in time and depth, the general history of the warmth 
cycle at the Garroch Head station appears at a glance. The section on Plate III., fig. 3, 
is interesting when compared with that for the Channel. The isotherms have no longer 
the simple form and uniform perpendicular direction, but the lagging of the deeper water 
is a conspicuous feature. The colours indicative of high temperature are widest at the 
top, but taper to a narrow band at the bottom, where the colours showing cooler water 
occupy proportionally more space. Just after the maximum and after the minimum 
temperature of the whole mass of water has been reached, the bands of colour lie 
vertically as in the Channel section. In the course of heating it appears by the section 
that the surface reached 50° on 15th June 1886, and remained above that temperature until 
the 19th November. The isotherm of 50° reached the depth of 30 fathoms on August 
27th, and the bottom (65 fathoms) on September 14th; so that the bottom was three 
months behind the surface in warming to a given extent. But temperature at the bottom 
only remained above 50° until December 10th, or only 20 days later than the surface. So 
that in cooling the lag of the season at the bottom was only one quarter as much as in 
heating. On this occasion the isotherm of 54° reached its deepest point (15 fathoms) 
on September 14th. 

In 1887 the surface was at 50° on May 12th : that isotherm had worked its way down 
to 30 fathoms by August 4th, and to the bottom by August 17th. By November 14th, 
or after six months, the surface temperature was again 50°, and the same temperature 
was reached at 30 fathoms on November 18th, and at the bottom by November 20th. 
Thus, while the warming at the bottom lagged more than three months behind the 
surface, the cooling was only six days behind. The rate of warming was interrupted by 
a comparatively cold spell early in July, but the isotherm of 54° reached 35 fathoms, its 
deepest point, on September 27th. 

The observations for the maximum of 1888 are not complete, but the isotherm of 50° 
never seemed to reach the bottom at all, and 54° only penetrated to 7 J fathoms. 

Comparing 1886 and 1887, we see that the warm period (denoting by this expression 
the time when the water-temperature was over 50°) lasted at the surface respectively for 
5 and 6 months, while the warm period at the bottom lasted respectively for barely 3 
and scarcely more than 3 months ; in other words, for just half the time. 

The slow penetration of heat giving a great inclination to the isotherms, scarcely 
extended below 35 fathoms, or half way down. In the lower half the temperature 
changed nearly homothermically ; as it did throughout for the greater part of the year. 

The difference from the Channel is shown by the reduction of the range of temperature 
in the lower layers, and its retardation in date. This is evidently due to reduced facility 
for mixing the deeper and the superficial layers of water. The deeper half of the water 
— that lying near or below the level of the bar separating the north-eastern branch from 
the main East Arran Basin — behaves very similarly to the Channel water, heating and 
cooling on the whole nearly simultaneously throughout its whole extent. The sharp 
contrast lies between this mass and the surface layers. The greater range of salinity is 



56 



DR HUGH ROBERT MILL ON THE 



associated with this result, it may be either as a cause or an effect. The thermal 
conditions would indicate that in the upper half of the water at Garroch Head the tidal 
or wind currents gave rise mainly to horizontal movement in sheets, while in the lower 
layers the movement, possibly on account of the slopes of the bottom, was more 
complicated, and had a considerable vertical component. 

Observations in Inchmarnoch Water. — This station is the meeting-point of the deep 
channels of the East and West Arran Basins, from which the greater depths run northward 
through the Central Arran Basin. 

Table XVII. — Temperature Observations in Inchmarnoch Water. 



No. . . 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


Date . . 


19-6-86 


6-8-86 


25-9-86 


18-11-86 


11-2-87 


30-3-87 


9-5-87 


16-6-87 


7-7-87 


12-8-87 


22-9-87 


15-2-88 


No. of Pts. 


9 


16 


7 


9 


9 


9 


6 


15 


15 


18 


10 


13 


Temp. . . 


44-4 


48-2 


50-7 


50-9 


44-1 


43-7 


44-7 


47-2 


47-8 


49-9 


52-1 


44-6 


Slope . . 


+ 2-5 


+ 8-4 


+ 5-5 


-1-4 


-0-5 


o-o 
(+2-1) 


+ 2-4 


+ 6-3 


+ 7-6 


+ 7-9 


+ 6-2 


-0-9 


H.D.* . . 


60 


5 





55 


83 


85 


55 


25 


35 








50 


h.t. . . . 


44-3 


45-6 




51-3 


44-1 


43-7 


44-4 


46-5 


46-3 






44-8 



* Assuming depth = 85 fathoms. 

The curves here call for no s£>ecial comment, being intermediate in character between 
those of the Brodick and Skate Island stations, and in all their leading peculiarities the 
description of the Skate Island curves is sufficient. 

Observations off Ardlarnont Point. — Observations at Ardlamont were taken in the 
spur of the Central Arran Basin, which runs up into the Kyles of Bute, and they give a 
good idea of the general temperature of the water entering that channel. 



Table XVIII. — Temperature Observations off Ardlamont Point. 



No. . 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 


14 


15 


Date . . 


20.4.86 


19.6.86 


6.8.86 


25.9.86 


16.11.86 


29.12.86 


7.2.87 


11.5.87 


15.6.87 


12.8.87 


24.9.87 


3.12.87 


13.2.88 


23.3.88 


20.9.88 


No. of Pts. . 


7 


4 


7 


7 


6 


6 


4 


6 


10 


10 


4 


6 


6 


6 


6 


Temp. . 


41-9 


45-1 


50-0 


52-4 


50-8 


467 


43-4 


44-6 


48-5 


52-2 


54-5 


48-9 


44-0 


42-6 


53-2 


Slope . 


+2-3 


+ 3-2 


+ 6-1 


+ 1-9 


-2-5 


-1-5 


-0-8 


+3-6 


+9-8 


+ 3-6 


+ 1-9 


o-o 


-1-5 


-0-6 


+ 2-7 



As the depth at the place of observation is only about 35 fathoms, it is unnecessary 
to note the thickness of the homothermic layer. The curves resemble the upper parts of 
those for Inchmarnoch, and, as a rule, show the characteristic homothermic type at the 
period of minimum, and clearly marked positive and negative slopes during the periods of 
rapid heating and cooling. Fig. 17, Plate XXV., shows a curious instance in which a very 



CLYDE SEA AEEA. 



57 



abrupt inflection in the Inchmamoch curve is repeated at the same position at the very 
bottom of the Ardlamont curve. This shows a remarkably horizontal arrangement of the 
isothermal sheets, as the stations are five miles apart. On this occasion there was no trace 
of extra heating in the shallow water ; in fact, the Ardlamont temperature was lower than 
that in the centre of the open water. The upjjer 28 fathoms of comparatively warm 
water was resting very abruptly and over a large area on the colder mass below. 

Observations off Skate Island. — The exact position is given by the bearing, centre of 
Skate Island, E. ^ S. 7 cables; and its depth 107 fathoms (Sections 16 and 19, C D, 
Plate 9 in Part I.) is the greatest of any part of the Arran Basin. It lies in the centre 
of the long depression which runs up the East Arran Basin, and is the deepest point 
in the whole Clyde Sea Area. 

The average density of water at 60° F. was as follows : — 



Mean 

Maximum 

Minimum 

Average Percentage of pure 1 
sea-water J 



Surface, 13 observations. 

. . 1-02446 
. . 1-02497 
. . 1-02373 

. . 94-0 



Bottom, 13 observations. 

1-02508 
1-02530 
1-02471 

96-5 



In the vertical section, during the period of observation, the proportion of pure sea- 
water was 96 "0 per cent., or in a normal year 95 "7 per cent. 

In estimating the homothermic depth, given below, the total depth is assumed as 
105 fathoms. 



Table XIX. — Temperature Observations off Skate Island. 



No. . . 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 


14 


15 


16 


17 


1 


Date . . 


28.8.78 


21.9.78 


25.6.7' 


)29.7.8i 


> 28.8.8. 


) 27.3.8* 


519.4.86 


21.6.86 


10.8.86 


17.9.86 


26.9.86 


16.11.86 


29.12.86 


7.2.S7 


28.3.87 


10.5.87 


15.6.87 


16.6.87 


No.oi'Pts. 


13 


11 


14 


4 


7 


9 


10 


7 


19 


7 


19 


15 


12 


12 


12 


15 


15 


15 


Temp. . 


51 '0 


53-2 


43-7 


50(?) 


49-7 


41-3 


41-6 


44-3 


47-3 


49-8 


49-8 


51-2 


47-2 


44-5 


43-8 


44-3 


46-6 


46-8 


Slope 


+ 9-4 




+ 8-2 




+ 6-6 


0.0 


+ 2-5 


+3.3 


+ 6-9 


+ 7-1 


+ 6-1 


-1-8 


-0-8 


-0-4 

/-10\ 


-o-i 


+ 2-0 


+ 4-4 


+ 5-6 


H.D. . 







75 




35 


105 


85 


85 


55 


20 





85 


85 


100 


105 


95 


45 


S5 


h.t. . . 






42-6 




47-6 


41-3 


41-3 


44-0 


45-2 


47-4 




51-4 


47-4 


44-5 


43-8 


44-2 


46-1 


44-1 


No. . . 


19 


20 


21 


22 


23 


24 


25 | 26 


27 


28 


29 30 


31 


32 


33 


34 


35 


36 


Date . . 


7.7.87 


8.7.87 


31.7.871 


4.8.871 


6.8.871 


2-9-87 5 


2.9.8718.12.87 


2.1.88 


7.1.88 


15-2-8828.2.88 


22.3.88 


6.4.88 


14.4.88 


16.5.88 


5.6.88 


19.10.88 


No.oi'Pts. 


14 


11 


17 


12 


n 


6 


12 


18 


12 


9 


15 


9 


15 


9 


6 


12 


9 


15 


Temp. . 


47-1 


47-5 


49-0 


49 -2 


49-7 


1 


51-2 


47-7 


46-5 


46-3 


44-6 


44-2 


42-9 


42-6 


42-5 


43-4 


44-1 


49-5 


Slope. . 


+ 6-6 


+ 7-0 


+ 8-8 


+ 6-3 


+7-2 




+4-9 


-1-6 


-1-2 


-0-9 


-1-1 


-2-9 


-0-3 


+0-1 


+ 1-5 


+2-3 


+ 4-2 


+2-2 


H.D. . 


55 


50 


40 


35 







35 


55 


60 


40 


75 


60 


95 


105 


75 


6 


55 


30 


h.t. . . 


46-2 


46-2 


46-5 


47-2 






49-2 


48-1 


46-9 


46-7 


44-8 


44-9 


43-0 


42-6 


42-3 


43-0 


43-0 


48-6 



VOL. XXXVIII. PART I. (NO. 1). 



H 



58 DR HUGH ROBERT MILL ON THE 

The importance of the Skate Island observations is exceptional, for several 
reasons. Being the deepest water in the Clyde Sea Area, it is the part of the Arran 
Basin most completely cut off from the sea, and consequently the characteristic thermal 
changes of the Basin should here be most readily detected. The station was 
also important because, from some happily situated landmarks, the exact spot where 
observations were made could be readily picked up at any time, and any tendency to 
drift while observing could be at once detected and checked. A set of observations had 
also been taken by Mr J. Y. Buchanan in the summers of 1878, 1879, and 1885, thus 
allowing of some interesting comparisons. 

The most striking feature of the temperature curves is that, with scarcely any 
exceptions, the lower 50 or 60 fathoms is straight and perpendicular, showing a 
predominating homothermic state in the deeper water. 

There were positive slopes on twenty-three occasions, zero slope once, and negative 
slopes only ten times. Compared with the Garroch Head observations, this shows that 
negative slopes are more difficult to establish in the deeper water. Otherwise the two 
stations are very similar. The maximum positive slope observed, 9° '4, is very nearly the 
same as for Garroch Head. The maximum negative slope was 2° '9, and only on this one 
occasion was the negative slope greater than 1°*8, while the positive slope was only twice 
less than that figure. Positive slopes over 4° "9 occurred fourteen times, — twice in June, 
thrice in July, five times in August, and four times in September. Negative slopes 
were only found in the months from November to March ; that is, in the months of 
rapid cooling and of minimum temperature. Positive slopes less than 4°*9 were shown 
three times in April, once in May, three times in June, and once in October ; that is, at 
the commencement of the periods of heating and cooling respectively. 

The rate of gain or loss of heat in the vertical section in a short interval of time 
could be studied on four occasions, when observations were made on successive days, or 
with an interval of a few days. Fig. 18, Plate XXV., shows curves 17 and 18 of Table XIX. 
representing the state of matters on the 15th and 16th June 1887. The observation of 
the 15th (curve A) was made at 12 o'clock, when the air-temperature was 57°*0, a 
light breeze was blowing from the north-west, and the tide was 4f hours' ebb. On the 
following day the observation was made at 15 h 30, when there was a very light southerly 
breeze with air-temperature 63° '0, and the tide about half an hour's flood, practically at 
low water. The change of temperature does not seem to be due to the movement of 
warmer water, for the up welling off Otter effectually isolates the surface layers of the 
Arran Basin from those of Loch Fyne, and, with the ebb tide, the effect of the warmer 
water in the seaward division could hardly be felt, although the fact of a distinct increase 
in surface-salinity on the second day hints that this might have been the case. The 
gain of heat, averaging nearly a degree for the first 20 fathoms (below which there was 
practically no change), may thus be taken to represent the heating effect of 21 hours' solar 
radiation, minus the cooling due to G|- hours of darkness ; and supposing the average rate 
of gaining heat in sunshine to be the same as that of losing it at night, the result would 



CLYDE SEA AREA. 59 

represent 14 J hours of sun-work. The actual gain of temperature throughout the whole 
mass was 0°*2, so that the rate of gain of temperature of 0'*014 per hour for the whole 
depth of 105 fathoms, or 0°'070 per hour for 20 fathoms. 

Fig. 19, Plate XXV., gives a similar pair of curves for 7th and 8th July 1887. The 
weather on this occasion was warm throughout, with a southerly or south-westerly 
breeze, interrupted by light squalls of hot air from the land. On the 7th, the 
middle of the observation was at 15 h 0, when the air-temperature varied from 63° to 66° 
in the calms and squalls. On the 8th the observation was at 17 ll 15, and the air- 
temperature between 68° and 70°, the breeze also being fresher. The tidal phase was 
thus practically the same on both days (l^ hours' ebb on the 7th, 1^ hours' ebb on 
the 8th), and the observations were 26^ hours apart. Of this time there were 19 hours 
daylight and 7 hours darkness, but the sky was frequently clouded. The two curves 
are identical below 60 fathoms, and from 30 to 60 fathoms run parallel and very 
close, the later being about 0°'2 warmer. The upper 30 fathoms are very peculiar. 
If on the second occasion only three observations had been made, viz., at 2, 12, 
and 31 fathoms, the two curves would have been put down as exact]y the same. 
The upper 30 fathoms of curve A form a perfect paraboloid — the characteristic curve 
of heating from above — except for a superficial cooling in the first 3 fathoms, which 
gives a sharp inflexion. The upper 2 fathoms of curve B complete the symmetry of curve 
A, but the rest of B is irregular, showing a curious local heating between 2 and 12 
fathoms, and a much more marked increase of temperature between 12 and 30. The 
latter portion of the curve is indeed of the inverted type. It is difficult to estimate the 
average temperature of curve B, as there is scarcely a sufficient number of points in the 
upper part, but the increase of temperature seems to be about 0°"4. On the assumption 
mentioned above, this would correspond to a rate of heating for the whole depth of 0°'033 
per hour of sunlight, more than twice that found for June. The soundings were, how- 
ever, made in squally weather, and the irregular distribution of temperature layers on the 
8th must be partly, perhaps mainly, due to the disturbing influence of a cross -channel 
breeze of hot air setting up irregular movements in the water. 

Fig. 20, Plate XXV., gives the vertical curves for Nos. 22 and 23 of Table XIX., observed 
on August 14th and 16th, 1887. Curve A on the 14th represents the state of temperature 
at 19 ll 40 when a light north-westerly breeze was blowing, curve B on the 14th at 15 h 15 
when there was a very light breeze from the south-west. On both occasions the sun was 
shining brightly. The observations were 44 hours apart, of which 26 were in daylight 
and 18 in darkness. Except for a slight excess of heating at the surface, and an 
apparent cessation of heating at 30 fathoms, the two curves were similar in form and 
only slightly divergent. They were coincident at the bottom, and the later curve 
showed 2° of warming at the surface. Were it not for the inflexion of curve A 
at 30 fathoms, which almost suggests a misreading of the thermometer by one degree, 
the amount of heating would diminish steadily from surface to bottom. Curve B 
shows almost the greatest positive slope observed at Skate Island. The average 



<)0 DR HUGH ROBERT MILL ON THE 

temperature of the vertical curve is greater by 0°"5 in B than in A. On the hypo- 
thesis of equal rates of heating and cooling in sunshine and darkness respectively, 
we find the rate of heating to average 0°'062 per hour of sunshine. This is twice 
the rate deduced for July, and four times that for June. It is impossible to believe 
that the heating power of the sun increases so enormously while its angle of incidence 
diminishes, and hence the hypothesis of assigning to local solar radiation the whole, 
or even a very large share, of the rise of temperature is obviously wrong. Pro- 
bably the real determining conditions are very complex. They must indeed ultimately 
depend on radiation, but we must look for an explanation to the general radiation 
over the whole area involved, over land whence the heat is carried by wind and 
surface water as well as over the water itself. Light on the question of the 
process of thermal change may be looked for rather in the study of mass temperatures 
than of such linear temperatures as are here noted. 

Figure 21, Plate XXVI. , gives the one case observed of the rate of cooling in a short 
interval of time, and the interval is as much as five days. In January, of course, the dura- 
tion of darkness was greatly in excess of that of daylight. In the case in question the time 
between the soundings contained 51 hours of darkness and only 21|- hours of light. The 
weather during the interval was usually overcast, with a good deal of rain and some 
southerly wind. On the 2nd the air-temperature was about 35°, on the 3rd about 44°, 
and on the 6th and 7th it rose in the afternoon to 49° or 50°. The great warmth of the 
later days is shown by a slight rise in temperature of the upper 10 fathoms ; but from 20 
fathoms to the bottom there is a steady fall, the earlier cold weather apparently having 
produced effects which were steadily and uniformly working clown. The inversion of the 
climatic change in the air greatly reduced the negative slope of curve B, but the mean 
temperature was o, 2 lower than that of curve A. Supposing, as before, that cooling by 
radiation proceeded at the same average rate in the dark as heating by radiation did in 
sunlight, and also that the total thermal change was due to radiation, the rate of cooling 
would appear to be 0° - 007 per hour. The disturbing causes are so numerous, however, 
as to deprive this conjecture of any quantitative value. 

A cross-section was made on September 23rd from Laggan Bay, on the Cantyre side, 
across the deep trough to Skate Bay, on the Cowal shore. The clay was hazy and dead 
calm, and there had been no wind to speak of for three clays. The dry-bulb thermometer 
in air read 49°'2, the wet-bulb 49° 3. The tide was about low water, being at the end 
of ebb when the Laggan Bay observations were made, and at the beginning of flood 
when the Skate Bay soundings were taken. It was practically slack water all the time. 
It is remarkable that the isotherms (fig. 22, Plate XXVI.) dip strongly toward the eastern 
side throughout the entire deptli of the water. The cause of this is not clear. There 
was no wind to set up a circulation ; nor was the heating on the eastern side due to the 
action of the shallow water, for the dip of the isotherms commenced westward of the 
deepest sounding. There was the appearance of upwelling on the eastern side, and of 
sinking of surface water on the western. No explanation of the phenomenon presents 



CLYDE SEA AREA. 



61 



itself: if the isotherms indicate a shearing movement in the water, the only efficient cause 
seems to be the tidal current, which at the beginning of flood may have carried warmer 
surface water along the west side, but this would not account for the westward dip of the 
deepest isothermal sheets. 

The larger seasonal effects, as shown at the Skate Island station, may be best brought 
out by grouping the curves of each year so as to show the stage of heating and cooling- 
arrived at at certain definite dates as equally spaced as possible. For this purpose it 
would be very important to have curves smoothed by taking the average of two at a 
short interval apart, but this is only possible in the cases cited above. Where exact 
averages cannot be obtained, the curves may sometimes be smoothed, in a manner 
not altogether arbitrary, by combining neighbouring observations, and when this is done 
the fact will be mentioned in the description. 

Figures 13 to 15 on Plate VII. show the results for the three seasons, corresponding- 
curves being similarly coloured. The dates to which the various curves correspond are 
as follows : — 



Table XX. — Typical Vertical Temperature Carves off Skate Island. 



Curve. 


Type. 


1886-87. 


1887-88. 


1888. 
























No. in 


Mean 


Time 


No. in 


Mean 


Time 


No. in 


Mean 


Time 






Table XIX. 


Date. 


Interval. 


Table XIX. 


Date. 


Interval. 


Table XIX. 


Date. 


Interval. 


I 


Minimal, . 


6 


27 March 


[ 23 days 

} 63 ,, 

|7»„ 
i 


15 


28 March 




31 


22 March 


1 39 days 














[ 43 days 






II 


Early Heating, . 


7 


19 April 




10 May 


} 37 „ 


Mean 33, 34 


30 April 










16 








36 ,, 


III 


Rapid Heating, 


8 


21 June 


Mean 17, 18 


16 June 


35 


5 June 


! 














80 „ 






) 


IV 


Maximal, . 


Mean 9, 10,11 


7 Sept. 


„ 23, 25 


4 Sept. 


1 

f 112 „ 






U36 „ 


V 


Early Cooling, . 


12 


16 Nov. 


j 70 „ 






36 


19 Oct. 


1 










43 „ 






) 








VI 


Later Cooling, . 


13 


29 Dec. 


} 40 ,, 


,, 26, 27 


25 Dec. 




















59 „ 








VII 


Final Cooling, . 


14 


7 Feb. 


,, 29, 30 


21 Feb. 


) 









The correspondence in date is not very close, but all the curves having the same 
number show a similar form, and belong to the same type. The first year is the most 
characteristic, and may be taken as generally typical of the order of temperature changes 
at this station. While the forms of the curves in different years are substantially the 
same, the position in temperature varies considerably. To some extent, this may be 
explained by the want of an observation at the actual date of maximum or minimum, 
but there is also a difference due to the different thermal amplitude of each season. 

The critical points, where one curve changes into another, are described in some detail 
for Garroch Head ; see figs. 12 to 15, Plates XXIV. and XXV. The minimum in each case 
is typically homothermic, and No. 2, the curve of early heating, is derived from it by a 
scarcely perceptible or quite imperceptible change in the lower layers, but a marked positive 



62 DR HUGH ROBERT MILL ON THE 

divergence in the upper 30 fathoms, showing a distinct paraboloid form, except that the 
upper end shows the 5-fathom layer of warmest water to be comparatively uniform in 
temperature. No. 3 shows homothermic heating throughout the whole depth below 20 
or 30 fathoms, the straight vertical curve being pushed forward nearly 3° in 1886 in 

63 days, 2° in 1S87 in only 37 days, but only about 0°"5 in 1888 in 36 days. The upper 
part of the curve is typically paraboloid, diverging positively from parallelism with the 
preceding curve toward the upper end. In 1888, however, the upper end presented an 
inverted paraboloid form ; which, together with the much slower rate of deep heating, 
showed some exceptional retardation in the progress of annual change. This may be 
related with the air-temperature (see curves, fig. 3, Plate XXII.), which was practically the 
same in 1887 and 1888 for April and May, but in June was nearly 5° lower in 1888 than 
in the preceding years. This lower air-temperature, or the causes which produced it, would 
account for the inversion of the upper part of the 1888 curve, but not for the slow rate 
of homothermic heating, which must be otherwise explained. In large part, the closeness 
of the three curves is due to the exact minimum not being represented. Curve 1 shows 
cooling still in progress, and curve 2 heating from the surface, while the lower part is 
colder than in 1. Curve 3 in 1887 shows a distinct approximation to the sickle shape. 
The intermediate minimum indicates that the rise of temperature had been less rapid at 
50 fathoms than anywhere else. If, as it seems reasonable to assume, homothermic 
change of temperature is effected by the complete vertical mixing of the water through- 
out the homothermic depth, while the positive or negative heterothermic condition of the 
upper layers is produced by positive or negative surface heat-exchange taking place too 
rapidly to be equalised throughout the mass by the movements in progress, it would 
appear that there was a freer circulation in the lower than in the upper half of the mass 
of water. This might result from a peculiar arrangement of the salinity of the water, or 
from a peculiarity in wind disturbance, but, unfortunately, no intermediate samples of 
water were collected on the occasion. In curve 4 we see the typical paraboloid form of a 
rapid rise of temperature through surface-heating. The homothermic condition has been 
entirely overcome, and from bottom to surface the water grows warmer more and more 
rapidly. Curve 5 (only properly shown for 1886) marks the passage of the annual 
maximum. The curve is negative, for rapid surface-cooling has set in, and it approxi- 
mates to the sickle shape possibly because heat is still being passed down by conduction 
in sufficient amount to partially overcome the tendency to homothermicity. The slope 
is, however, very slight. The curve in question shows a check to surface-cooling at the 
time of observation by the very slight slope of the upper 10 fathoms. Compared with 
curve 4, it shows most rapid cooling to have taken place at the surface, and most rapid 
heating at the bottom, while at 17 fathoms the temperature w T as the same in both cases. 

The process of transition between the forms 4 and 5 is of very great interest, and may 
be indicated thus. Until the equinox, there is a large positive gain in the surface heat 
exchanges of the water by solar radiation, and until about the middle of August by 
contact with warm air. The surface density being much lower, through its less salinity, 



CLYDE SEA AREA. 63 

than that beneath, the effect of evaporation in this climate is not sufficient to increase the 
density through increasing salinity so much as the increased temperature reduces it. 
Hence the hottest surface layer tends to float and become still hotter, giving a very steep 
positive slope to the curve. The mass of the water tends toward homothermicity by the 
mixing effect of direct and indirect wind and tidal action, but the conduction of heat 
downward from the warm, highly heterothermic surface layer gradually raises the 
temperature, reducing the heterothermic layer, and giving a positive slope to the whole 
curve. The greater the positive slope the more rapid is the flow of heat downward by 
conduction, and the curve of density in situ becomes similar to a mirror image of that of 
temperature, thus assuming a stable form and retarding the mixing processes which 
involve vertical circulation. 

The mean difference of density determined at 60° F. between the surface and bottom 
water at Skate Island was — 0"00052, the bottom being denser. This corresponds to the 
ordinary state in hoinothermic conditions. For the maximum positive temperature 
slope observed, viz., 9°'4, this difference is increased to —0*00219 ; while for the 
greatest negative slope observed, viz., 2° -9, the difference is -0"00018. In the latter 
condition it is apparent that the resistance to vertical movement on account of the 
density of the layers, due to salinity and temperature, is less than one-tenth as great as in 
the former, and a very slight increase of surface density would determine a downward 
convection current. Inasmuch as the slope of a curve is estimated from the average 
temperatures of layers of five fathoms thick, it is plain that the actual surface layer must 
often be cold enough to cause an inversion of the density gradient and lead to downward 
convection in a place like Skate Island, where the salinity gradient is so very slight. 
These considerations fully explain the small negative slope, the parallelism, and the rapid 
displacement negatively of the four curves for cooling, Nos. 5, 6, 7, and No. 1 of the 
next year. 

The thermal conditions of themselves would bring about an approach to homo- 
thermicity, and they are here reinforced by the other agents working in that direction — 
the action of wind and tide. 

The time-changes of temperature are shown in fig. 1, Plate II., in the same way as 
for Garroch Head, only, on account of the smaller number of observations, the horizontal 
scale is reduced one-half. It closely resembles the Garroch Head diagram. The isotherm 
of 50° was reached by the surface on July 8th, 1886, and had worked its way to the 
bottom by October 28th. In cooling, the temperature of 50° was reached by the surface 
on November 8th, and on the bottom by November 30th, the isotherm, which required 
110 days to work down in rising, requiring only 21 days to work down in falling. Gauged 
by this isotherm, the warm season at the bottom was one month, while on the surface it 
was four. The isotherm of 54° reached the deepest point (7|- fathoms) on September 1 5th. 

In 1887 the surface was above 50° from May 28th to November 6th, a period of 5 
months and 10 days, but the isotherm of 50° never reached the bottom at all, its utmost 
penetration being to 62 fathoms on September 24th. The isotherm of 54° reached 8 



<54 



DR HUGH ROBERT MILL ON THE 



fathoms, its deepest point, on August 1st. This failure of the heat to penetrate in 1887 
is very remarkable, as the water-temperature at the preceding minimum had not been so 
low as the year before, and the unprecedented heat of June might be expected to have a 
great effect. The Garroch Head diagram shows no trace of this effect ; and the only hint 
conveyed is by the tendency of the June 1887 vertical curve to assume the sickle shape. 
The temperature section for June (No. X., Plate X.) shows a large mass of cold water at the 
head of the Central Arran Basin, tapering away off Skate Island, and disappearing a little 
south of Inchmarnoch. By July this had disappeared. The existence of the intermediate 
layer of cold water, however, shows that the usual vertical movements leading to mixture 
and equalisation of the temperature in the lower layers had by some means been restricted. 
The density affords no clue to the cause of this, as the water, both at surface and bottom, 
was considerably above the average, and the difference between them was very much less 
than usual. The calmness of the season might be brought forward to explain the effect, 
but this should have produced an even more marked appearance of the intermediate 
minimum in Loch Fyne, where none was observed. From the incomplete data for 1888, 
it seems to have been a year resembling 1887, except that the maximum bottom tempera- 
ture was even lower. 

Observations off Kiljinan Bay. — The soundings were made in the axis of the Arran 
Basin, off Kilfinan Bay, Otter House bearing E. 2 miles 2 cables, and the depth 80 
fathoms. About this position the depths are very irregular, but for 14 miles down the 
Basin there is never less than 75 fathoms in the centre. The density of the water was 
only occasionally observed, but we may assume it as intermediate between Skate Island 
and Otter I. 

The curves resemble those for Skate Island, though somewhat less regular, and it is 
unnecessary to discuss them farther in thi? place. 



Table XXI. — Temperature Observations off Kiljinan Bay. 



No. . . . 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


Date 


29.3.87 


10.5.87 


15.6.87 


7.7.87 


15.8.87 


23.9.87 


16.12.87 


3.1.88 


14.2.88 


22.3.88 


4.6.88 


19.10.88 


No. of Pts. . 


9 


12 


9 


9 


12 


9 


12 


12 


9 


9 


12 


9 


Temp. . . 


43-9 


44-6 


46-6 


47-8 


49-6 


51-7 


48-1 


46-6 


44-8 


43-2 


44-8 


49-9 


Slope . . 


+ 0-2 


+ 2-0 


+ 4-4 


+ 5-8 


+ 5-8 


+ 4-9 


- 2-7 


-0-9 


-1-0 


-0-9 


+ 4-7 


+ 0-1 


H.D.* . . 


75 


55 


35 


20(?) 








35 


25 


65 


60 


30 


75 


h.t. . . . 


43-9 


443 


45-2 


46-3 






48-9 


46-8 


44-9 


43-3 


43-2 


49-9 



Depth assumed as 75. 



Observations at Otter I. — Observations were usually made with Otter Beacon bearing 
N.E. by E. 7 cables, where the depth was 30 fathoms. This point was just outside 
Otter Spit, where the tide runs strongly into and out of the Gortans Basin of Loch Fyne. 



CLYDE SEA AREA. 



65 



Observations were, however, often made nearer the entrance and farther from it. 
The average density of the water was as follows : — 



Surface, 5 observations. 


Bottom, 5 observations. 


Mean, . . . 


. 1-02461 


1-02497 


Maximum, . 


. 1-02486 


1-02507 


Minimum, . . 


. 1-02416 


1-02470 


Average percentage of pure 








93-0 


95-7 



In vertical section, 95*2, or in normal year, 94 - 9. 



Table XXII. — Temperature Observations at Otter I. 



No. . . . 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


Date 


19.4.86 


21.6.86 


10.8.86 


11.8.86 


28.9.86 


17.11.86 


29.12.86 


4.2.87 


29.3.87 


10.5.87 


15.6.87 


7.7.87 


No. of Pts. . 


7 


7 


7 


4 


4 


6 


6 


6 


6 


3 


6 


7 


Temp. . . 


42-0 


444 


49-9 


50-4 (?) 


51-9 


50-8 


47-4 


44-7 


44-1 


45-8(?) 


47-4 


49-9 


Slope . . 


+ 1-6 


+ 1-8 


+ 2'9 


+ 24 


+ 0-9 


-1-3 


-1-7 


-1-5 


+ 0-3 


+ 05 


+ 3-2 


+ 31 


Depth . . 


38 


33 


25 


14 


15 


15 


28 


53 


33 


15 


20 


22 



The main interest of this station arises from its position on the seaward side of the 
steep barrier which shuts off Loch Fyne from the Arran Basin. The discussion of density 
observations showed that there is a marked upwelling of deep water about this point, and 
temperature observations amply confirm the fact. The evidence from surface temperature 
will be given when speaking of Loch Fyne, but the clearest proof is shown by the rise of 
the isotherms to the surface at Otter on the temperature sections (Plates VIII. to XV.) 

The effect of the tidal current running north up the wide Central Arran Basin, and 
finding no outlet except the narrow entrance of Loch Fyne to the north-east, seems to 
be to drag the deep layers of water up the slope, and so give rise to a back-flow on the 
surface, or in the still deeper layers. It is largely to this disturbance of the equilibrium 
of the mass of water in the Arran Basin, and to the similar action of other sloping shores, 
that I am inclined to attribute the continual mixing, which tends to maintain a homo- 
thermic state in the deep water. The tidal reaction-currents would naturally be powerfully 
reinforced by wind, and possibly modified to some slight extent by variations in 
density. 

Temperature Sections of the Arran Basin. — The outstanding features of the mass 
distribution of temperature on eighteen trips were laid down in the form of isotherms 
upon a much exaggerated profile of the section from the Channel through the East and 
Central branches of the Arran Basin and Loch Fyne to Cuill. These sections, 
coloured according to the principle already described, are useful in showing the nature 

VOL. XXXVIII. PART I. (NO. 1). I 



66 DR HUGH ROBERT MILL ON THE 

and order of the changes going on. The observations were, however, so few that when 
the great extent of the Arran Basin and Plateau are considered it appears impossible to 
utilise the sections for any reasonably accurate measurement of the mean temperature of 
the region, and accordingly I do not reproduce the calculations provisionally arrived 
at, and published in 1887 # in a preliminary paper dealing with the first year's work. 
An attempt was made to allow for some of the probable errors in an estimate of this 
kind, but the result was unsatisfactory. In the case of the narrower divisions, however, 
the necessary allowances could be made, and they are discussed in detail. The sections, 
which are practically those of the Arran Basin and its neighbouring regions, are given 
in Plates VIII. to XL The following is a brief summary of the main features : — 

1. April 1886. — The only isotherms shown on the section are those of 43° and 42° ; 
beneath about 15 fathoms the temperature varied from 42° to 41 0, 5. The section presents 
a perfect picture of the uniform minimum temperature just beginning to rise at the surface. 

2. June 1886. — Eegular warming is here shown from above downward, and still 
more markedly from the ocean inward. The isotherms all dip strongly seaward, showing 
the effect of the warm Channel water forcing its way into the Arran Basin. The 
Central Arran Basin is much colder than the Western Branch at the same depth, and 
there is an evident up-draught of cold water from below at Otter. 

3. August 1886. — The same general order of temperature distribution is clearly 
shown. Warming is still taking place from above downward, and from the sea inward, 
the deeper isotherms showing an obvious relation to the irregularities of the bottom. 
The up-draught at Otter does not appear to affect more than the superficial 30 fathoms. 

4. September 1886. — The conditions here are similar to those in the August 
section, perhaps a little more pronounced, on account of the higher temperature of 
the surface water. 

5. November 1886. — Here rapid cooling is shown. The Channel water being homo- 
thermic at 50°, is rapidly chilling the lower layers of the deep water of the Arran Basin, 
which remains above 51°, but the Channel water is warming the surface of the Arran 
Basin, which has fallen below 50°, and is colder toward Loch Fyne. The upwelling at 
Otter is marked by the warm deep water coming nearest the surface at that point and 
overflowing into the Gortans Basin of Loch Fyne, which, at the bottom, is warmer than 
any other water at the same depth. 

6. December 1886. — Here rapid cooling has gone on in the Arran Basin from the 
surface down, most rapidly in the centre. The Channel water not having cooled so fast, 
is now warmer than that of any part of the Basin, and the isotherms at the mouth of 
the Arran Basin dip landward. In November the Channel water was aiding seasonal 
change, and by its high salinity and low temperature rapidly affected the whole Arran 
Basin. But cooling by surface exchange, and downward convection has now outstripped 
it, and the Channel water is left relatively warmer, feebly retarding the inevitable work 
of advancing winter. At the head of the Basin the isotherms dip seaward, showing the 

* Proceedings, Glasgow Philosophical Society, xviii. (1887), 332-356. 



CLYDE SEA AREA. 67 

up-draught of the warm bottom layer raising the temperature of the upper strata. At 
this end of the Basin the last remnant of water as warm as that of the Channel is found, 
an interesting instance of the effect of configuration. 

7. February 1887. — Here we find that the Channel water has again cooled down 
below that of the Arran Basin and is chilling it rapidly from the sea, while surface 
cooling at the upper end of the Basin seems relatively retarded. This effect may 
perhaps be accounted for by the middle of winter being the rainiest season, and February 
the month of minimum surface salinity. Hence in February 1887 (and the condition 
was similar in November 1886) the density gradient offered unusual resistance to down- 
ward convection, sufficient to restrict the operation of cooling from the surface to down- 
ward conduction and the chance action of wind. On this account the Channel water, 
cooling steadily, is once more furthering seasonal change by mixing, in virtue of its 
higher salinity, with the Arran Basin water. 

8. March 1887. — The minimum has now passed. It was not so low as in 1886, 
and Loch Fyne did not come to so low a temperature as the Arran Basin, another 
important difference. Now the Channel has warmed up rather more than the mass of 
the water in the Basin, on which, however, it seems to have produced little effect. The 
surface water of the Basin is also warming by surface exchange of heat, and the last 
remnant of the warm deep layer appears at the head of the Arran Basin as it did in 
December 1886. 

9. May 1887. — Heating has here proceeded gradually from the surface downward, 
and from the ocean inward. At the Skate Island sounding and also in Loch Fyne there 
was evidence of a patch of lower temperature surrounded by warmer water. The 
appearance suggests that the vertical movements of circulation follow more or less the 
configuration of the bottom, descending from the Plateau to the deepest part, creeping 
up the slope at the head of the Basin, and returning seaward in the upper layers. This 
rotation of the water in a vertical plane, if it exist, would account for a portion of colder 
water being left in the centre. 

10. June 1887. — Here we see a much higher temperature throughout than in the 
previous June, and a more marked heterothermicity in the water. The surface stratum 
of warm water deepens in a very characteristic way when it passes from the practically 
homothermic Channel to the centre of the West Arran Basin, and then runs away rapidly 
in the Central Arran Basin, deepening again over Loch Fyne. The peculiar condition 
of the Plateau on this occasion is treated in detail on p. 24. The equally interesting 
mass of cold water, resting against the slope at the head of the Arran Basin, and 
melting away into warm water above, below, and seaward, has been remarked on at p. 
23. We may look on this wedge of cold water as the dwindling mass attacked equally 
by the in-draught from the seaward and warmer parts of the Arran Basin from beneath 
and by the downward conduction of heat from above. From some cause which does 
not appear, the customary upwelling along the terminal slope does not seem to have 
occurred, and so the cold mass has not been entirely isolated as in May. 



68 DR HUGH ROBERT MILL ON THE 

11. July 1887. — Apparently more influence is exerted in this section by downward 
conduction from the hot surface layers than is usual. The up-draught at the head of the 
Basin is less marked, and at the mouth of the Basin the cold deep water seems to be up- 
welling and creeping across the Plateau under the mass of warm Channel water, which, 
pouring into the Basin, produces its customary heating effect a little beyond the position 
where that effect usually begins to be noticed. 

12. August 1887. — Except for its higher temperature, this section closely resembles 
that for August 1886. In both, the deep water of the West Arran Basin has been raised 
above that of the central branch at the same depth, but in this the effect of the warm 
Channel water cannot be so clearly traced, because no observation was taken on the inner 
edge of the Plateau. The upwelling at Otter is very clearly marked. 

13. September 1887. — This corresponds closely with the section for September 1886. 
It shows the temperature at the actual maximum observed at the time when the warm 
salt water of the Channel was producing its maximum effect throughout the Basin. The 
manner in which the ridge off Loch Eanza abruptly separates the deep water of the 
western branch from that of the central is exceptionally well brought out. It is interest- 
ing to note that some less complete sections which were drawn through the East Arran 
Basin show a marked similarity to the series now being described. Although there is no 
bar across the deep channel which runs from off Largybeg to off Kilfinan Bay, the upper 
section of the Basin shows every mark of isolation in the slower response to temperature 
change, a result due solely to distance from the powerful influence of the Channel water. 

14. December 1887. — This section illustrates best the utter uselessness of isotherms 
to delineate temperature distributions when the range is small. Here the whole mass of 
water is almost homothermic at 48°, the isotherms of 47° and 49° only appearing for a 
short distance at the head of the Basin. The Channel was much warmer than the Arran 
Basin, and except in Loch Fyne surface-cooling was being propagated directly throughout 
the mass of water. 

15. January 1888. — Here there is a somewhat unusual distribution of temperature. 
The surface of the Arran Basin is cold, the cold layer being thinnest at the head where 
the Otter upwelling raises warmer water, and thickest on the Plateau which it completely 
covers, cutting off the warmer homothermic water of the Channel from that of the deep 
parts of the Basin. 

16. February 1888. — The water on the Plateau appears to continue colder than that 
on either side, the greater part of the Arran Basin being filled with nearly homothermic 
water of the same temperature as that in the Channel, the process of cooling having 
evidently gone on unchecked by the usual freshening of the surface water. 

17. March 1888. — Considerable cooling had gone on since February, and the result- 
ing distribution of temperature is curiously irregular. The temperature on the Plateau 
was again lower than that on either side, and it had exercised a strong cooling effect on 
the neighbouring parts of the Arran Basin. At the head, on the Otter slope, there was an 
area of considerably warmer water, resembling on a smaller scale the arrangement shown 



CLYDE SEA AREA. 69 

in June 1887. Looking at the section generally, the Plateau as a whole seems a centre 
of cold, on receding from which to the north and the south along the surface — and still 
more rapidly on deeper planes — the water grows warmer. The rapid cooling since 
February, the very low temperature of both these months, and the absence of a layer of 
very cold surface water, point to the great part which must have been played by down- 
ward convection caused by increase of density by chilling in the surface layers. 

18. April 1888. — Here again, as in the whole series of the winter 1887-88, the coldest 
water radiates from the inner slope of the Plateau. The difference in temperature is, 
however, very slight, and the conditions closely resemble those of April 1886, the 
water being practically homothermic, and the mean temperature almost the same in the 
two occasions. It represents the typical arrangement of minimum temperature. 

The succeeding temperature trips were not sufficiently systematic to allow of the 
observations made during them being utilised for drawing sections. 

In order to compare the distribution of temperature with depth in the eastern and 
western branches of the Arran Basin, the diagram fig. 23, Plate XXVI., shows the Skate 
Island soundiDg (S) in the centre, with the isotherms connecting it to Inchmarnoch (I) and 
Brodick, East Arran Basin (B) drawn to the right, and those connecting it to Inchmarnoch 
and Carradale, West Arran Basin (C) to the left. The profile is approximate only. If 
the section were folded along the line of the Skate Island sounding, and then folded in 
the opposite direction along the two Inchmarnoch lines, as shown in the figures at the 
lower left-hand corner of fig. 23, the run of the isotherms would show the true relations 
of the two southern branches, while the central part would carry on the lines up 
the northern branch of the Basin. Fig. 23 shows that, in June 1887, the Eastern 
Branch was, at the same depths, considerably colder than the Central. It also shows 
how the included wedge of cold water (see longitudinal section for June) stretches 
in a rapidly-thinning slice as far as Brodick in the Eastern branch, but does not enter 
the Western branch at all. It is thus seen to be purely a product of the configuration of 
the Central branch of the Basin. 

Fig. 24, Plate XXVII., is a similar diagram for September 1887, and is even more 
instructive, — the sounding off Loch Ranza, on the ridge separating the Western from 
the Central trough, being inserted. Down to 50 fathoms, or practically to the level of 
this ridge, there is little difference between the Eastern and Western branches, both being 
somewhat warmer than the Central, but beneath 50 fathoms the effect of configuration is 
brought out in a most interesting manner. The temperature of 51° scarcely occurs 
in the Western branch, and 50° does not enter it at all, although that isotherm runs up 
the Eastern and Central branches at an average depth of 63 fathoms. Below 80 
fathoms the temperature in the Eastern branch is below 49°, and this reaches to 
Inchmarnoch, accounting for the curious patch of cold water in the section for September 
1887 (No. XIII. Plate XL), but the Central Basin remains warmer throughout, the lowest 
temperature in the Skate Island Depression being 49°'l. 



70 



DR HUGH ROBERT MILL ON THE 



Seasonal Range of Temperature in the Arran Basin. — The mean temperature 
curves for seasonal change at each of the Arran Basin stations were drawn on a large 
scale, and combined with a view of getting the true mean annual movement of tempera- 
ture for the whole mass of the deeper water. The curves for Largybeg, Brodick, and 
Garroch Head were drawn on one sheet, time being abscissae, and temperature ordinates. 
A mean curve was drawn freehand through the points determined, mainly the very 
numerous points of the Garroch Head curve. This gave an approximation to the 
mean annual conditions of the East Arran Basin, so far as regards the mass of the 
deep water, the curve embracing two maxima and three minima. 

The curves for Inchmarnoch, off Loch Ranza and Carradale, made a second though 
less complete set, the mean drawn through which followed most closely the Carradale 
points, and this may be taken as typical of the West Arran Basin. 

Finally, the curves for Skate Island, Kilfinan, and Otter I. were combined graphically 
on a third sheet, and represented the conditions of the Central Arran Basin. The 
three mean curves were then traced off on the same piece of tracing paper, with different 
coloured inks, and a mean, drawn by eye through the three, was taken as representing 
the seasonal change of temperature of the mass of the deep water of the Arran Basin as 
a whole. 

Table XXIII. — Monthly Mean Temperature of Mass of Water in the three 
Divisions of the Arran Basin from Curve. 

1886. 



Station. 


Jan. 


Feb. 


Mar. 


April. 


May. 


June. 


July. 


Aug. 


Sept. 


Oct. 


Nov. 


Dec. 


Arran B. East 








42-2 


44-0 


46-0 


48-4 


50-6 


51-9 


51-5 


49-6 


46-1 


„ West 








42-4 


43-8 


45-6 


48-2 


50-1 


51-2 


51-2 


49-7 


47-1 


,, Central 








42-3 


43-4 


44-8 


47-2 


49-3 


50-6 


51-0 


49-8 


47-4 


„ Mean 








42-3 


43-5 


45-3 


47-7 


49-9 


51-3 


51-4 


49-7 


46-7 












1887. 














Arran B. East 


43-9 


43-5 


43-4 


44-3 


46-2 


48-4 


50-9 


53-0 


53-0 


51-4 


48-4 


45-9 


„ West 


44-4 


43-5 


43-6 


44-8 


47-0 


49-6 


50-9 


52-0 


52-0 


50-7 


48-7 


46-5 


„ Central 


44-9 


44-1 


43-8 


44-2 


45-6 


47-4 


48-7 


50-4 


50-8 


49-6 


48-5 


46-7 


„ Mean 


44-5 


43-7 


43-5 


44-4 


46-2 

18£ 


48-4 
8. 


50-2 


52-0 


52-1 


50-4 


48-5 


46-3 


Arran B. East 


44-6 


43-2 


42-0 


42-8 


















„ West 


44-6 


42-8 


42-3 


42-8 


















,, Central 


45-4 


44-0 


42-6 


42-8 


















„ Mean 


44-8 


43-4 


42-3 


42-8 



















CLYDE SEA AREA. 71 

The East Arran Basin shows the greatest range of temperature and a slightly earlier 
phase than the others. This is brought about by a higher maximum, all the curves 
comma- close together at the minimum. At the maximum the curves are most widely 
separated, the West Arran Basin coming second in each case, and the Central branch 
last. The three curves preserve this order during the annual rise of temperature, but 
reverse it while falling and at the minimum, when the Central branch is warmest and 
the Eastern coldest. The curves cross in April while the temperature is rising, imme- 
diately after the minimum, and in October or November when falling, shortly after the 
maximum. . The mean temperature for each month, taken from the curve, is given for 
the branches and the Basin as a whole in Table XXIII. 

Fig. 25, Plate XX VII., showing the seasonal variation of the temperature of the air as 
the average of the whole Clyde Sea Area, of the whole mass of water in the Arran Basin, 
and of the superficial layer of 5 fathoms, may be usefully compared with fig. 5, Plate 
XXIII. , giving the same data for the Channel. It must be remembered, however, that 
although the Arran Basin results are supported by much more numerous data than 
those of the Channel, the regular homothermic change in the Channel makes its curve 
probably more correct than that of the Basin. 

Comparing the temperature of the whole mass of water, we see that it started on April 
15th, 1886, from the same minimum as the Channel, 42° ; and on October 1st it reached 
its maximum value of 51°'6 (3°"4 lower than the Channel, and twenty days later). This 
rise of 9°*6 in 165 days corresponds to a mean storage of o, 058 per day, one-third less 
than the Channel rate. The rate of fall of temperature increased much more gradually 
than in the Channel. By March 1st, 1887, the minimum temperature, 43°*6, was reached, 
slightly lower and a little earlier than the Channel. This corresponded to a loss of 8° in 
151 days, or at the rate of o, 053 per day, a rate one-fifth less than that of the Channel. 
On September 2nd, 1887, the maximum of 52° # 2 was reached (4° colder and 16 days 
earlier than the Channel), a rise of 8°"6 in 186 days, at the rate of 0°*046 per day, 
the ratio to the Channel conditions being the same as in the previous year. The fall of 
temperature proceeded more gradually, the minimum, 42°'5, being reached on March 
20th, 1888, 9°'7 being lost in 199 days, or at the rate of 0°-049 per day. 

The near approach to equality in the time of heating and cooling of the mass of 
water in the Arran Basin is remarkable when compared with the disparity shown in the 
Channel. 

Warming 1886. Rate. Cooling 1886. Rate. Warming 1887. Rate. Cooling 1887. Rate. 

Channel, . . 147 days, +0°-090 171 days, 0°-065 189 days, 0°'065 217 days, 0°-062 
Arran Basin, 165 days, + 0°058 151 days, 0°053 186 days, 0°046 199 days, 0°-049 

The rate of change of temperature in the Arran Basin varied, as the curve shows, 
more regularly and uniformly than in the Channel. Whereas the periods of heating 
and cooling in the Channel were as 100 to 115 on the average of two years, they were 
equal on the average in the Arran Basin. The minima were synchronous, but the 



72 DR HUGH 110BERT MILL ON THE 

maxima occurred about a month later in the Basin. The curve of air-temperature cut 
that of mean water-temperature rather after the maximum, instead of before it, as in the 
Channel. 

During the period of rising temperature, the air was warmer than the surface layer 
of water for 147 days in 1886 and for 125 in 1887 ; while the air was cooler than the 
water on 224 days in the cool season 1886-87, and 232 days in 1887-88, giving an 
average of 134 days of air warmer than water and 228 cooler, comparing with 134 
warmer and 237 cooler for the Channel, the cycle being somewhat over a year in this 
instance. 

The surface-water curve in fig. 24 is compiled in a less satisfactory way than the 
curve for mass temperature. It is nearly a mean between the mass curve and the air 
curve during the period of heating, and shows a tendency also to occupy an inter- 
mediate position at the minimum. During cooling, however, the surface and mass 
water curves coincided in 1886, but the surface curve remained higher until near 
the minimum in 1887. The former is probably the more characteristic form. 

Interpolating probable values for the first three months of 1886, we are able to arrive 
at the following averages for the year : — 

In 1886, . . Air =46-2 ... Surface Water =47-4 ... Mass of Water =46 -4 

In 1887, . . Air =47-0 ... Surface Water =49 "3 ... Mass of Water =47-5 

The " surface " water being the top layer 5 fathoms deep. 

Here we see the mass of the water on the average of two years one-third of a degree 
warmer than the air, while the surface water averaged 1°'7 warmer, thus closely 
approximating to the condition in the Channel. It appears that on the average 
of the whole year the Arran Basin exercises a warming influence upon the air, although 
not to such an extent as the Channel. 

Loch Fyne. 

Loch Fyne is an extension of the Central Arran Basin so far as surface water is con- 
cerned, but the depressions of which it is composed are barred off in such a way as to 
isolate the deeper water more completely than in any other part of the Area. It may be 
said that the deep water of Loch Fyne is more effectively isolated from the Arran Basin 
than the Arran Basin is from the open sea. Within the Otter Bar the bed of Loch Fyne 
deepens into the comparatively flat and shallow Gortans Basin scarcely more than 
34 fathoms deep, which in turn is shut off from the deep Upper Basin by a ridge at 
Minard, on which rises a series of islands separated by narrow channels. Beyond this 
second barrier there is a steep descent to depths of over 75 fathoms, and then a gradual 
rise to the head of the loch at Cuill. Numerous observations were made in Loch Fyne, 
and both temperatrue and density were more fully studied there than in any other 
division of the Area of equal size. Each station has a certain individuality with regard 



CLYDE SEA AREA. 



73 



to the movements and thermal changes of its water, and the form and variations of the 
temperature curves are of some interest. Speaking broadly, one would expect from the 
configuration that Loch Fyne should differ physically from the Arran Basin in the same 
way as the Arran Basin differs from the Channel, but to a greater degree. 

It is to be noted that I restrict the name "Loch Fyne" to what is sometimes called 
Upper Loch Fyne. On ordinary maps and on the Admiralty chart the name is marked 
as it is popularly applied to the whole surface of water stretching northward from Inch- 
marnoch, thus including the Central Arran Basin. 

Observations at Otter II. — The station termed Otter II. has Otter Beacon bearing 
S. by E. 2 cables, depth 20 fathoms. (Section 18 K, PI. 9 of Part I.) It is just inside 
Otter Spit, where the tide runs very strongly, and on the sill of the Gortans Basin. The 
average density of water at the station is as follows : — 



Surface, 4 observations. 

Mean, 1-02434 

Maximum, .... 102483 
Minimum, .... 102383 
Average percentage of pure sea-water, 930 



Bottom, 4 observations. 

102479 

102498 

102451 

95-7 



In vertical section 95'2, or in normal year 94 - 9 
The water is thus considerably fresher than that of Skate Island in the Arran Basin. 



Table XXIV. — Temperature Observations at Otter II. 



No. . . . 
Date . . . 
No. of Points 
Temp. . . 
Slope . . 



10.8.86 

7 

50-3 

+ 2-8 



2 

17.11.86 

6 

500 

-11 



3 
5.2.87 

3 
44-3 
-03 



4 

10.5.87 

6 

45-4 

+ 1-4 



5 
15.8.87 

8 
52-0 
+ 2-5 



6 
23.9.87 

6 
532 
+ 1-5 



7 

16.12.87 

6 

46-7 

-0-8 



8 
3.1.88 

6 
46-1 
-0-3 



9 

14.2.8* 

6 

44-4 

-0-3 



10 

22.3.8! 

6 

42-9 

-0-9 



11 

16.10.88 

6 

49-9 

-0-3 



The temperature curves are usually straight or else very irregular, and this is also the 
case to a less extent at Otter I. The appearance is largely due to the difficulty of keep- 
ing station in the tideway, and the consequent uncertainty of taking two consecutive 
soundings in exactly the same spot. 

The greatest positive slope shown was 2° '8, and the greatest negative slope — 1°*1. The 
usual sequence of forms was shown, the homothermic, usually with a negative tendency, 
preponderating at the minimum. The curves of heating were usually rather irregular 
paraboloids, but No. 4 was a good example of an inverted curve. The best specimen of a 
contorted curve was No. 6, which occurred at the maximum of 1887, and showed alternate 
strata from the surface downward of warmer and colder water (fig. 26, Plate XXVIII.). 

In 1886, a number of surface temperature observations were made in passing Otter 

VOL. XXXVIII. PART I. (NO. 1). K 



/4 DR HUGH ROBERT MILL ON THE 

Beacon.* They were made as rapidly as possible in buckets of water drawn for the 
purpose at intervals of a minute, or in some cases less. On April 19, while passing up 
the loch in the "Medusa," we observed between 15 b 12 and 15 h 25, passing the Beacon 
at 15 h 22. The tide at the time was about half-ebb, running out of the loch with about 
its maximum velocity. At 15 h 12 the surface temperature outside Loch Fyne was 43° "4, 
and this diminished to 42°'9, 43 o, 0, 42°7, 43 o> (at 15 h 16l), 18, 18J, 19£, then remained 
at 43° until 15 h 22, when at the Beacon it rose to 43° '2, and retained that value through- 
out the Gortans Basin. Here the ebb tide produced a perceptible cooling of the surface 
water just outside the loch, the total amount being about half a degree, indicating an 
upwelling of the slightly colder lower layers. 

On June 22nd, 1886, observations were made at longer intervals coming down the loch. 
A surface reading was taken every ten minutes from 14 h 50 to 15 h 40, passing the Beacon 
at 15 h 20, within an hour of high tide, the current setting in slowly. The resulting read- 



ings were 



Beacon. 
N.E. 47°-9, 47°-0, 46°"5, 45°-7, 45°0, 46°-7. S.W. 

The minimum occurring, as before, outside the loch entrance. 

The soundings on June 21st (see Loch Fyne, Section II., Plate XII.) bring out an 
exactly similar distribution as prevailing at 15 h 25, with the tidal phase rather more than 
an hour earlier, and a stronger current consequently running in. 

On August 10th at 16 h 20-17 h a set of surface temperatures was taken which 
showed a fall from 52°'l to 51°"3, and a rise to 52°'2 in passing the Beacon; although 
a mile further up the loch, the temperature again fell to 51°*6. The tide was 1|- hours 
flood, setting in strongly. 

On the following day about 16 h the observations were repeated in leaving the loch, 
with the tide about low water, and the fall of surface temperature was found to be from 
52°'5 to 51 0, 6, with a subsequent rise to 52°"6 outside. (See Section III., Plate XII.). 

On September 26th the Beacon was passed going up the loch at 15 h 6. Observations 
every ten minutes for an hour previously showed a uniform surface temperature of from 
53°"4 to 53°*2 to prevail all the way from Kilfinan Bay, but at 1 5 h 8 it dropped to 52 0, 9 ; 
then at intervals of ten minutes going up Loch Fyne the readings were 53°"0, 53°"0, 
52° # 9, and 5 2° 7. Here all that was shown was that the surface water in Loch Fyne was 
about half a degree colder than that outside, the slight change taking place at the entrance. 
The day was calm and dull, the tide was about the end of flood, within an hour of high 
water. 

On 16th November 1886, the Beacon was passed at 13 b 20 going up the loch with 
tide i\ hours flood ; the temperature ranged from 49°'8 to 49°*4, reaching that minimum 
at the Beacon, and then rising to 49°'5 and 49°*6. The effect was almost too slight to 
be relied upon ; but on the following day (see Section V., Plate XII.) it was visible to 
precisely the same extent. 

* Jouru. Scot. Met. Soc, vol. viii., No. 4, pp. 108-110. 



CLYDE SEA AEEA. 



75 



Observations off Gortans Point. — This station is fixed by Loch Gair entrance bearing 
JS T .W. by N. 9 cables. The depth is 35 fathoms (Section 18, L, PL 9 in Part I.) in the 
centre of the shallow and uniform Gortans Basin, which serves as a sort of trap between 
the Upper Basin of Loch Fyne and the Arran Basin. 

The density of the water is as follows : — 



Surface, 9 observations. 
Mean, .... 1-02398 
Maximum, . . . 102452 

Minimum, . . . 102224 

Average percentage of pure sea-water, 92 - 7 

In vertical section 945, or in normal year 94*2. 



Bottom, 9 observations. 

1-02467 

1-02493 

102403 

94-9 



Table XXV. — Temperature Observations off Gortans Point. 



No. . . . 
Date . . . 
No. of Points 
Temp. . . . 
Slope . . . 



1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


19.4.86 


21.6.86 


22.6.S6 


11.8.86 


28.9.86 


16.11.86 


29.12.86 


5.2.87 


29.3.87 


10.5.87 


7 


3 


11 


7 


7 


8 


6 


6 


12 


6 


42-2 


45-81 


44-9 


49-8 


51-6 


50-1 


46-4 


44-3 


44-1 


45-8 


+ 1-0 


+ 3-6 


+ 2-7 


+ 2-9 


+ 1-6 


-1-3 


-1-3 


-0-5 


+ 0-4 


+ 0-9 



11 

15.6.87 

9 

47-9 

+ 2-8 



No. . . . 

Date . . . 
No. of Points 
Temp. . . . 
Slope . . . 



12 


13 


14 


15 


16 


17 


18 


19 


20 


21 


7.7.87 


15.8.87 


16.8.87 


23.9.87 


16.12.87 


3.1.88 


7.1.88 


14.2.88 


22.3.88 


4.6.88 


9 


12 


7 


6 


6 


6 


6 


6 


6 


6 


49-5 


51-2 


51-6 


53-1 


47-3 


46-0 


46-1 


44-9 


42-9 


45-7 


+ 4-2 


+ 3-7 


+ 3-4 


+ 1-7 


-0-8 


-0-4 


+ 0-3 


o-o 


o-o 


+ 1-6 



22 

16.10.8 

6 

49-9 

-0-1 



As a rule, the temperature at Gortans was more extreme than at Furnace on the slope 
of the Upper Basin, being higher in the warming months, lower in the cooling. 

The small slope of the curves is remarkable, the greatest positive value being 4° - 2, 
the greatest negative value, 1°"3. The range is almost entirely confined to the upper 
10 fathoms, and often to the upper 5 fathoms, the lower 25 fathoms being usually 
either homothermic or of very gentle and uniform slope. In fact, the general character 
of the curve resembles that of the Arran Basin rather than that of barred lochs. 
The size of the entrance and exit to the Gortans Basin relatively to its depth, taken 
together with the strong tides which traverse it and the vertical mixing at the Otter 
Bar, are quite sufficient to account for this effect. In discussing the temperature sections 
it will be shown that the Gortans Basin plays quite a distinct part in the seasonal 
temperature changes. 

Curve 3 is interesting, taken in connection with the fragment of Curve 2 (see fig. 27, 
Plate XXVIII.), showing a mixing and cooling of the upper 5 fathoms, while the rest of 



76 



DR HUGH ROBERT MILL ON THE 



the curve is practically unchanged. On the 21st June 1886 (Curve 2) the wind was 
light from the north, tide half hour ebb ; on the 22nd (Curve 3) squally from the south, 
and the tide was about half flood. These different conditions seem sufficiently to explain 
the change. 

Curves 13 and 14 (August 15th and 16th, 1887) are interesting in being, so far as 
the defective data of Curve 14 can show, precisely alike, with one small exception. This 
is a break in the uniform paraboloid by 3 fathoms of straight line, just above 20 fathoms 
in No. 13, just below it in No. 14. Curve 12 is reproduced as one of the most perfect 
specimens of a positive paraboloid. 

Curves 1 7 and 18, for January 3rd and 7th, ] 888, have almost the same mean tempera- 
ture (46° and 46°*07). The former is above 46° below 10 fathoms, and below 46° 
above that depth, while in the latter this relation is inverted. But since the extreme 
temperatures in No. 17 are 45° # 8 and 46°'2, and those in No. 18 are 46°*4 and 45°*9, 
there is scarcely room for detailed comparison. 

The homothermic change of the lower layers in this basin, where there is an excep- 
tionally complete system of interchange of water, strongly confirms the explanation of 
the modus operandi of this form of change, arrived at from the study of the Arran Basin. 

Observations at Minard and Paddy Rock. — At Minard, Loch Fyne is con- 
stricted, and the surface divided into several channels by a group of islands. The two 
chief channels in which observations were sometimes made are "Minard" on the 
western shore, with a maximum depth on the sill of 12 fathoms, and " Paddy Eock " on 
the eastern shore, which is somewhat wider, and has a maximum depth of 18 fathoms. 
These channels separate the deep Upper Basin of Loch Fyne from the Gortans Basin. 

The density of water may be assumed as the mean of that at Gortans and Furnace. 

Table XXVI. — Temperature Observations at Minard and Paddy Bock. 



No. ... 
Date . . . 
No. of Points 
Temp. . . . 
Slope . . . 
Placet • • 



1 


2 


2(a) 


3 


4 


5 


6 


7 


8 


9* 


10 


5.2.87 


29.3.87 


29.3.87 


10.5.87 


15.6.87 


7.7.87 


15.8.87 


23.9.87 


6.1.88 


6.1.88 


16.10.88 


3 


6 


6 


4 


4 


6 


8 


3 


6 


9 


4 


44-3 


44-1 


44-2 


45-5 


49-6 


51-8 


52-2 


52-9 


46-4 


46-5 


49-9 


-0-8 


+ 0-4 


+ 0-2 


+ 0-6 


+ 2-3 


+ 5-7 


+ 3-0 


+ 0-8 


-0-1 


+ 0-4 


00 


M 


P 


M 


M 


P 


P 


P 


P 


P 


M-P 


P 



* Deep water. 



t M = Minard Channel. P = Paddy Rock Channel. 



These curves show no notable peculiarities, except that the change of temperature 
is mainly confined to the superficial 5 fathoms. The great range of No. 5 is remarkable : 
surface temperature 60°'4, at 4 fathoms 50 o, 6, and at bottom (15 fathoms) 49°*2. 



Observations at Furnace. — The position where observations were made is defined 



CLYDE SEA AREA. 



77 



by the bearing Fairy Hill S.E. ^ E. 2^ miles, which is in mid-channel opposite Furnace 
Quarry, and the depth is 35 fathoms. This point is on the threshold of the Upper 
Basin of Loch F^yae, which deepens abruptly to the east, while to the west there is 
a stretch of 3 miles, averaging 35 fathoms in depth along the axis, with very slight 
irregularity, then rising to form the Minard bar. 

The density of the water was found to be as follows : — 



Surface, 9 observations. 
Mean, .... 102380 
Maximum, . . . 102452 

Minimum, . . . 102134 

Average percentage of pure sea-water, 91 



Bottom, 9 observations. 

102463 

102488 

102421 

947 



In vertical section 941, or in normal year 93"8. 



Table XXVII. — Temperature Observations at Furnace. 



No. . . . 

Date 

No. of Points 

Temp. . . 

Slope . . 



Actual Slope 



1 
19.4.86 

7 
42-2 
+ 0-8 



2 3 

22.6.86 jll.8.86 

7 15 

44-2 j 47-8 

+ 2-1 | +8-1 
+ 2-9 



0-8 I 



4 5 6 7 

27.9.861 16.11.86 I 29.12.86 I 5.2.87 



10 

49-3 
+ 6-5 



8 
49-7 
+ 0-2 
0-6 



-U'D | 

+ 0-8 I 



6 6 

47-0 I 44-6 
-1-4 1-2-3 



-1-8. 

+ 0-4 f 



8 

29.3.87 

9 

44-2 

+ 0-5 



9 

10.5.87 

6 

45-0 

+ 0-8 



10 

15.6.87 

12 

48-2 

+ 4-5 



No. ... 
Date . . . 
No. of Points 
Temp, . . 
Slope . . . 



Actual Slope 



11 


12 


13 


14 


15 


16 


17 


18 


19 


8.7.87 


15.8.87 


23.9.87 


16.12.87 


3.1.88 


6.1.88 


14.2.88 


22.3.88 


25.8.88 


14 


11 


9 


9 


6 


6 


9 


6 


12 


49-9 


50-9 


52-2 


47-9 


47 3 


47-1 


45-6 


43-2 


50-1 


+ 8-8 


+ 7-0 


+ 3-9 


-2-0 


-0-3 


-04 

-0-6 i 
+ 0-2 1 


-1-5 
-2-5 i 
+ 1-0 / 


-0-7 


+ 7-5 














... 



20 
16.10.* 
6 

49-5 
+ 1-0 



The observations at Furnace show on the whole less range than those at Dunderawe, 
both places occupying similar positions at either end of the Upper Basin, and the depths 
being equal. The mean temperatures were somewhat higher in winter and somewhat 
lower in summer at Furnace. This greater uniformity is well shown in Curve 9 (May 
1887) of each set (compare fig. 28, Plate XXVIIL, and fig. 36, Plate XXIX.). For 
Furnace the curve is a straight line of mean 45° - reduced range + 0° "8, and for 
Dunderawe it has mean 45°'8 and reduced range -I- 5°*2. 

At Furnace there is a marked tendency towards S-shaped curves, more distinct than 
those seen in the Gareloch, and showing a tendency, as in No. 10 (fig. 28), to pass into 



78 DB, HUGH ROBERT MILL ON THE 

the contorted form. This is brought about in many cases by a very steep gradient at 
the bottom of the curves, such as is rarely shown elsewhere. Curve 10, for example, 
shows a fall of 1°*4 in the last 3 fathoms, where the gradient is almost as steep as in 
the surface layers, and far steeper than at any intermediate point. Curve 11 also shows 
a marked steepening of the gradient, a concave parabola below 20 fathoms. 

In No. 12, the steepest gradient in the whole curve lies between 28 and 30 fathoms ; 
but Curve 13 (fig. 28), shows this peculiarity most strikingly. In this curve (23rd 
September 1887) there is from the surface to 5 fathoms a fall of 1°'6, from 5 to 32 
fathoms a net fall of 1°"1, while from 32 to 34 fathoms the fall is as great as 3° "8 in only 
2 fathoms. This peculiarity, only noticeable between June and September 1887, and 
comparison of the sections of the loch, shows a narrowing of the zone of rapid change of 
temperature towards the S.W. end of the basin, the layer of rapid change of temperature 
being usually much less clearly marked. The upper layers of water are seen by the 
section to be more fully mixed or less affected by land at the Furnace end of the Basin 
at all times of the year. 

There was only one case of short-interval observations, Nos. 15 and 16, on January 
3rd and 6th, 1888. The mean temperature fell from 47°'3 to 47°'l, or at the rate of 
0°*7 per day. The fall was 0°'4 in the top 5 fathoms, 0°'3 in the bottom 5 fathoms, 
and, except for an irregular rise between 5 fathoms and J 5 fathoms, was fairly uniform 
for the rest (fig. 28, Plate XXVIII. ). 

The observations at this station are most valuable, as showing the effect of the 
sudden steepness of descent of the loch's bed on the physical condition of the 
water. 

Observations off Strachur and Inveraray. — It is convenient to consider the two 
deepest stations at which observations were made in the Upper Basin of Loch Fyne 
together. The station about midway between Strachur and Kenmore was in the centre 
of the Basin, and practically at its deepest part, although patches of equal depth occur 
between it and Furnace. The depth is 75 fathoms, being 15 fathoms deeper than the 
observing point between Inveraray and St Catherines. The latter may be looked on 
as in the deepest water of the Basin also, as the slope along the axis is very uniform. 
While the deepest water off Strachur lies nearly in the middle of the loch, that off 
Inveraray is very much nearer the south-eastern than the north-western shore. This is 
partly because of the widening of the loch by the large bay known as Loch Shira, and 
partly because of the shallowing of the north-western margin by the deposits brought 
down by the rivers Aray and Shira. 

The following summaries of the conditions at the two points show that the water at 
Inveraray is of slightly lower salinity throughout than at Strachur. The difference at the 
bottom is very slight, that at the surface considerably greater on account of the inflowing- 
rivers. 

At the Strachur station the position of observation was Fairy Hill S.W. by S. ^ S. 



CLYDE SEA AREA. 



79 



2 miles 8 cables, and the depth 75 fathoms. (Section 18 D, Plate 9, in Part I.) The 
density of the water was : — 



Surface, 12 observations. 

Mean, 1-02246 

Maximum, .... 102446 
Minimum, .... 101197 
Average percentage of pure sea-water, 85'7 

In vertical section 93'3, and in normal year 93'0. 



Bottom, 12 observations. 
1-02458 
102517 
102430 

94-8 



For Inveraray the position was Inveraray Castle N.N.W. (on with Aray Bridge) 1 
mile. Depth 60 fathoms. The density of the water was : — 



Surface, 12 observations. 

Mean, 102130 

Maximum, .... 102439 
Minimum, .... 101311 
Average percentage of pure sea-water, 83'2 

In vertical section 92'7, or in normal year 92 - 3. 



Bottom, 10 observations. 

102456 

102487 

1-02404 

946 



Table XXVIII. — Temperature Observations off Strachur. 



No. ... 
Date . . 
No. of Points 
Temp. . . 
Slope . . 

Actual Slope 



1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 


14 


19.4.86 


20.4.86 


21.6.86 


11.8.86 


25.8.86 


27.9.86 


17.11.86 


29.12.86 


4.2.87 


29.3.87 


10.5.87 


15.6.87 


8.7.87 


15.8.87 


7 


7 


12 


21 


10 


13 


18 


9 


10 


17 


15 


15 


14 


13 


, 42-1 


42-1 


44-2 


45-6 


46-2 


47-2 


47-5 


46-2 


45-4 


44-6 


45-0 


46-4 


46-8 


47-9 


+ 0-4 


+ 0-6 


+ 4-6 


+ 8-0 


+ 9-2 


+ 8-3 


+ 4-0 


-1-3 


-2-6 


-1-0 


+ 3-1 


+ 5-8 


+ 8-3 


+ 9-6 


1 ••' 




+ 6.2 1 
-1-6 C 


+ 8-7) 
-0-7} 


+ 9-3) 

-o-i s 




-1-5) 
+5-5 ) 


-3-9) 
+ 2-6 ( 


-3-0 * 
+ 0-4/ 




+ 3-6) 
-0-5 ) 









No 

Date . . . 
No. of Points . 
Temp. . . . 
Slope . . . 

Actual Slope 



15 


16 


17 


18 


19 


20 


21 


22 


23 


24 


25 


26 


27 




23.9.87 


5.11.S7 


7.11.87 


17.12.87 


14.2.88 


28.2.88 


22.3.88 


7.4.88 


4.6.88 


18.7.88 


25.8.88 


16.10.88 


18.10.88 




12 


12 


9 


15 


18 


9 


9 


9 


9 


15 


12 


12 


15 




48-9 


48-3 


48-4 


47-5 


45-6 


44-5 


43-8 


43-1 


44-3 


45-3 


46-9 


46-8 


47-0 




+ 8-1 


+ 2-1 

-2-3) 
+ 4-4 ( 


+ 4-1 

-0-1) 
+ 4-2/ 


-1-2 

-3-3) 

+ 2-1) 


-1-1 

-2-6) 


+ 0-2 


-0-8 


+ 0'8 


+ 3-0 


+ 4-4 


+ 11-2 


+ 5-7 
-0-2) 

+5-9 ) 


+5-6 

-0-2) 

+ 5-8 \ 





hO 



DR HUUH ROBERT MILL ON THE 



Table XXIX. — Temperature Observations off Inveraray. 



No 

Date 

No. of Points . . . 

Temp 

Slope 

Actual Slope . . . •! 

No 

Date 

No. of Points . . . 

Temp 

Slope 

Actual Slope . . . < 



1 2 

19.4.8621.6.81 

7 15 



41-7 
+ 0-7 



43-6 

+2-S 

+ 4-7) 
-1-9) 



3 

10.S.S6 

19 

i.v: 

-r9-5 

+ 10-4 t 
-0-9 f 



4 
24.8.86 

7 

46-4 

-:-l0-8 

+11-11 

-0-3 ) 



16.9.86 
4 

47-7 ■>. 
+ 10-2 



6 
17.9.862; 

11 
47-6 
+ 9-3 



i 

86 
12 

477 
+ 8-4 



8 

17.11.86 
15 

48-3 

+2-5 

-2-01 

+4-5 ] 



9 

30.12.86 

12 

46-8 

-1-0 

-2-6) 
-1-6 j 



10 
5.2.87 

10 
45-3 
-2-7 



-3-2 

+ 



1} 



11 

29.3.87 

17 

44-6 

-0-5 



12 

10.5.87 

12 

45-0 

+ 4-1 

+ 4-6) 
-0-5 ( 



13 

16.6.87 
16 
46-6 

+ 7-3 



14 
8.7.87 

18 
47-1 
+ 10-3 



15 


16 


17 


18 


19 


20 


21 


22 


23 


24 


25 


26 


27 


28 


16.8.87 


23.9.87 


13.10.87 


5.11.87 


17.12.87 


14.2.88 


23.3.88 


4.6.88 


25.8.88 


27.8.88 


1.9.88 


17.10.88 


26.8.89 


3.9.89 


15 


10 


9 


12 


16 


15 


9 


9 


15 


12 


6 


12 


13 


13 


48-4 


49-1 


49-0 


49-1 


47-5 


45-7 


43-6 


44-3 


47-5 


47-7 


49-7? 


47-0 


48-1 


48-6 


+ 9'9 


+ 7-3 


+5-0 


+ 1-3 

-2-0) 
+3-3 \ 


-2-8 

-3-9) 
+1-1 1 


-1-1 

-2-6) 
+1-5 ] 


-0-8 


+ 2-6 


+ 12-1 


+ 12-1 


+ 10? 


+ 5-5 


+ 8-4 


+ 6-6 



Out of the twenty-one occasions when observations were made at both stations, there was 
no difference in the mean temperatures of vertical soundings five times, the temperature 
at Strachur was higher five times (0°'9 as a maximum), and that at Inveraray was higher 
eleven times (0°'8 as a maximum). On the whole, the mean temperature of the water at 
Inveraray was o, l higher than at Strachur. Asa rule, the temperature at Inveraray 
was higher in the warmest months, and approached equality or became colder than at 
Strachur during the cold months. The slope of the curves was always the same at both 
stations, but the amount of slope was on the whole 0°*07 greater for Inveraray than for 
Strachur. On two occasions the slope had the same value, nine times it was greater at 
Strachur (maximum difference 1°'8), and ten times it was greater at Inveraray (maximum 
difference 2 o, 0). The slope was greater at Inveraray than at Strachur only during the 
warming months — from May to September ; during the cooling months it was greater at 
Strachur, surface heating being stronger at the former, surface cooling at the latter place. 

Change of Temperature in short intervals of time. — There are five cases of observa- 
tions at the same point within two days, three of these being at Strachur and two at 
Inveraray. 

Observations on 19th and 20th April 188G at Strachur, Nos. 1 and 2 of Table XXVIII. 
— The two observations gave identical results below 1 fathoms, the water being practically 
homothermic at 41 0, 9 ; and the upper 5 fathoms were at 42° '2 on the first occasion, and 
42°'5 on the second (fig. 29, Plate XXVIII.). The narrowness of Loch Fyne and the 
numerous disturbing causes, such as wind, rivers, and rainfall, make it hopeless to attempt 
to measure the effect of radiation in the way suggested for the Skate Island observations. 

Observations on 5th and 7th November 1887 at Strachur, Nos. 1G and 17 (see fig. 30, 
Plate XXVIII.). — The mean temperature was higher by 0°'l on the second occasion, but 



CLYDE SEA AB,EA. 81 

this result may be due to the fact that No. 16 was fixed by 12 points, No. 17 by only 9. 
No. 16 showed a rapid rise from 45°*9 on the surface to 50°"0 at 10 fathoms, a fall increasing- 
more rapidly as it deepened to 47° at 53 fathoms, and then a gradual fall to 45°*5 at the 
bottom. No. 17 was practically constant at 49°"8 from surface to 25 fathoms, a possible 
maximum of 49°"9 being shown at 20 fathoms. Below this depth the curves practically 
coincided. The upper 25 fathoms of No. 16 gave an irregular parabola with mean tempera- 
ture 49°"5 ; this is straightened in No. 17 into a vertical line with mean temperature 
49° - 8 ; the disturbance practically does not extend below 25 fathoms, and shows a definite 
warmino - as well as mixing in the upper layers. The 5th was calm, while on the 7th 
a strong north-easterly wind blew down the loch. The curves of the same date for Cuill 
and Dunderawe may be compared with those for Strachur, and the relation between these 
is well brought out in Sections XIV. and XV., Plate XIV. 

Observations on 16th and 18th October 1888, curves 26 and 27 (fig. 31, Plate 
XXVIII. ). — These show a rise of 0° # 2 in two days. The curves were very fully traced 
out, and are remarkably irregular. The upper part of both for 10 fathoms shows mean 
temperature of about 49° '8, nearly uniform, then a uniform convex parabola descending 
to 44°'l at 50 fathoms in No. 26, and a concave parabola, joined at 25 fathoms by 5 
fathoms of uniform temperature to a regular convex parabola descending to 44°*2 at 50 
fathoms in No. 27. This shows two areas of considerable warming about 20 fathoms and 
35 fathoms. On the 16th the observation was made at 15 h 45 in a calm : the temperature 
of the air was 51°*3, and during the earlier part of the day there had been a very light air 
from the south-west. October 17th was calm, overcast, and a little cooler, while on the 
18th the observation was made at 12 h 30, with the air temperature at 51°"2, the weather 
misty, and a freshening breeze blowing from the south-east. There is nothing in the record 
of weather to account for the remarkable heating at 30 fathoms ; and were it not that the 
temperature recorded at 35 fathoms points in the same direction, one would be tempted 
to look on that at 30 as a misreading of one degree. 

Observations on 16th and 17th September 1886 at Inveraray, Nos. 5 and 6 in Table 
XXIX. (fig. 32, Plate XXVIII. ). — The data for curve No. 5 are too incomplete to allow of 
comparison with No. 6, but those of No. 7 for 27th September (see fig. 33) are exception ally 
complete. Below 50 fathoms the three curves are very much alike, the temperature being- 
close to 44°. In the ten days elapsing between Nos. 6 and 7 the surface layer showed slight 
cooling, and the intermediate layers slight warming, but the total change of temperature 
was only a rise of 0°*1. These two are the most perfect examples found of S-shaped 
curves, i.e., compound heterothermicity without intermediate maxima or minima. They 
are compounded of two parabolas, the upper concave, the lower convex to the origin. 
The limiting form of such a curve would represent the superposition of a mass of uniformly 
hot water upon a mass of uniformly cold water. The maximum change of temperature 
with depth took place about 25 or 30 fathoms, where a fall of 3°'4 took place in 
5 fathoms. 

Observations on 25th and 27th August 1888, Nos. 23 and 24 (fig. 34, Plate XXIX.) 

VOL. XXXVIII. PART I. (NO. 1). L 



82 DR HUGH ROBERT MILL ON THE 

at Inveraray. — These are the curves of greatest slope (12°*l) observed in Loch Fyne, and 
represent the maximum heating effect. They are the nearest approaches to simple positive 
paraboloids, and bear every evidence of being due to surface heat being propagated uni- 
formly downward. Omitting the superficial fathom, which showed some cooling on the 
27th, the upper layer of water showed well-marked heating down to 25 fathoms, and below 
that depth a possible slight cooling, although the temperature was probably the same on 
both occasions in the lower half. On the whole, the result of the interval of two days was 
a rise of o, 2 in temperature. The 25th was a bright, warm day (air-temperature 62°7 at 
time of observation, 10 h 0), with a light, southerly breeze. The weather on the 27th was 
similar, though the ah- was cooler (57°'0 at the time of observation, I7 h 20), and the breeze 
rather stronger. The gain of temperature for the first 20 fathoms may be put down as 
0°"5 ; and as there were 3G hours of daylight and 19^ hours of darkness between the 
observations, on the hypothesis of equal rates of gain aud loss of heat (see p. 58), the 
effect of solar radiation and contact with warm air was to raise the temperature at the 
rate of 0°'03 per hour to the depth of 20 fathoms, or 0°*012 per hour for the whole depth. 
These are much smaller values than were obtained in similar cases of double observations 
at a short interval of time at Skate Island, and equally valueless. Observations at Inveraray 
were made by me from a rowing boat on 26th August and 3rd September 1889, Nos. 27 and 
28 (fig. 35, Plate XXIX.). August 26th was calm, with overcast sky, and air-temperature 
56° when the observation was taken at ll h 30. The tide was about high- water. In the 
afternoon the weather became squally. The intervening week was warm, with light breezes 
and little rain, except on the 2nd September, when a strong easterly breeze was blowing. 
On the 3rd the sky was overcast, the weather calm and hazy, with a very light air from 
the south-east, and the tide at the time of observation was within an hour of low-water. 
The result of the week's warm weather was a rise in the mean temperature of the 
sounding from 48°*1 to 48° '6. The two curves crossed at 10 fathoms, the upper layer 
having cooled about 0°*7 on the average, while the 50 fathoms beneath had been warmed 
up almost uniformly by o, 4. This plainly points to a considerable mixing of the water 
in the interval, either by wind or tide, or both. No salinity observations were made. 
On the first occasion the temperature gradient was exceptionally uniform from surface 
to bottom, the curve being between a straight line and a simple paraboloid ; but on the 
second occasion the gradient of the first 20 fathoms had been greatly reduced (clear 
evidence of mixing), that of the lower 30 fathoms was unchanged, and the intermediate 
10-fathom zone showed a marked accentuation, the curve having become a compound of 
two paraboloids. 

Cross Section at Inveraray. — A cross section of Loch Fyne at Inveraray, from the 
usual observing station to Inveraray pier, was made in the autumn of 1889 on two 
occasions, August 26th and September 3rd. The isotherms were practically parallel and 
horizontal in both cases, although in the interval there had been strong winds. Both 
the days of observation were calm. 

Seasonal Variations. — The seasonal variations of vertical temperature in the deepest 



CLYDE SEA AREA. 



83 



water of Loch Fyne may be traced by means of the curves, as at Skate Island. Instead 
of taking the Inveraray or Strachur observations alone, the two are combined, with the 
effect of considerably smoothing the curves (see figs. 16 to 18 on Plate VII.). The dates 
are selected to correspond with those at Skate Island ; the references to the curves are 
given in Table XXX. The numbers correspond with those for Skate Island (Table XX.). 



Table XXX. — Typical Vertical Temperature Curves in Loch Fyne. 



6 

> 

u 

B 
O 


1886-87. 


1887-88. 


1888. 


Keference 
Table 


Date 
(Mean). 


Time 

Interval 

Days. 


Reference 
Table 


Date 
(Mean). 


Time 

Interval 
Days. 


Reference 
Table 


Date 
(Mean). 


Time 

Interval 

Days. 


I 

II 

III 

IV 

V 

VI 

VII 


XXVIII. 

1-2 
3 

4 
6 

7 
8 
9 


XXIX. 

1 

2 
3 
6-7 
8 
9 
10 


April 19 
June 21 
Aug. 11 
Sept. 25 
Nov. 17 
Dec. 29 
Feb. 4 


63 

51 
45 
53 
42 
37 


XXVIII. 

10 
11 
12-13 
15 
16 
18 
19 


XXIX. 

11 

12 

13-14 

16 

18 
19 
20 


March 29 
May 10 
June 26 
Sept. 23 
Nov. 11 
Dec. 17 
Feb. 14 


53 

42 
47 
89 
49 
36 
59 


XXVIII. 

21-22 
23 

25 

26-27 


XXIX. 

21 

22 

23-24 

26 


March 28 
June 4 
Aug. 26 

Oct. 17 


42 
68 
83 

52 



While the form of the curves is different in detail for each year, there is sufficient 
similarity between them to suggest that the year 1886-87 may be taken as a type. The 
only difficulty which this year presents is the low temperature and perfect homother- 
micity of its minimal curve. If that could be set aside, the difference in range varies in 
a very interesting way with depth. At the surface the seasonal amplitude may be as 
much as 20°, at 10 fathoms it is only 10°, at 35 fathoms 5°, and at 70 fathoms only 2°. 
Plotting these values, and extending the curve to the depth of 105 fathoms, the annual 
range would come out as only 1°, and at 150 fathoms it would practically vanish. The 
contrast of this condition with that at Skate Island is striking. There it would appear 
that the range of seasonal temperature at the bottom is scarcely less than that at the 
surface, and its value may be taken as at least 10°. The regime of the deep water as 
regards temperature is thus entirely different in the two basins. The physical 
differences are that Loch Fyne is smaller, shallower, more completely invested by high 
land, more completely barred off from the open sea, and with a greater difference 
between the density of surface and bottom water than is the case in the Arran 
Basin. The most striking difference in the curves is the absence of homothermic 
change of temperature in Loch Fyne except in very rare cases. Considering homo- 



^4 DR HUGH ROBERT MILL ON THE 

thermic change of temperature in deep water as a sign of free mixture of the water, 
we are justified in accepting the curious form of the Loch Fyne curves as evidence of 
the normally restricted circulation in the deep water of that basin. The homothermic 
agencies being restricted, fuller play is given to the influence of radiation and the contact 
of warm air or warm water in producing temperature changes. The curves appear to 
be in large measure conduction curves, convection being reduced to a minimum. The 
average difference between the density of surface and bottom water at Strachur was 
0-00212, and at Inveraray '00326, compared with 0-00052 at Skate Island. No fall of 
temperature would be sufficient to invert the density gradient due to salinity, and thus 
the conditions in Loch Fyne resemble a vessel of water the temperature of which 
depends on a layer of oil floating on the surface. This question will be discussed more 
fully when speaking of the temperature sections of Loch Fyne. 

The characteristic feature of these curves is their tendency to assume a sickle shape. 
How this form is derived from the homothermic will be explained when dealing with 
the sections, and, for the present, we may start with Curve 2, which in 1886 showed a 
much more pronounced intermediate minimum than in 1887. Above 15 fathoms this 
curve shows rapid heating in progress from the surface downward. Curve 3, after the 
lapse of 51 days in 1886, 47 in 1887, and 83 in 1888, shows no change of temperature 
at the bottom, nor in 1886 within 15 fathoms of the bottom, but an increasing rise of 
temperature as the surface is approached, the curve assuming the form of a paraboloid, 
significant of the most rapid stage of surface-heating. No. 4, after 45 days in 1886, and 
89 days in 1887, shows an approximation to the S-shape. In 1886 this curve almost 
exactly conforms to the " oceanic " type. The lower part is a parabola showing the con- 
tinued descent of heat, but the bottom fifteen fathoms remain unchanged in temperature. 
Surface-cooling having set in, the upper layers, losing heat in both directions, have given 
to the upper part of the curve the form of an inverted parabola. A zone of rapid change 
of temperature occurs between 25 and 30 fathoms. In No. 4 for 1887 later heating- 
seems to have turned the inverted parabola into a direct one again. Curve 5 is a very 
fine example of the negative sickle shape, produced by the rapid loss of heat from 
the surface, and the more gradual transference of heat downwards, although the bottom 
temperature was not yet raised. Curve 6 is of similar form, but displaced in a negative 
direction, except at the bottom, where the temperature now begins to rise. In 1886 
there was a zone of very rapid change of temperature between 45 and 50 fathoms. The 
progress of surface-cooling has now made the temperature of the upper layers colder than 
the remains of the previous cold at the bottom. Curve 7 in 1886 is an approximation 
to a negative parabola, the bottom water having practically reached its maximum while 
the surface is at the annual minimum. In 1887 there had been rapid and almost 
homothermic cooling to the bottom. The transition of Curve 7 to 1 of the following 
year was in both cases brought about by nearly homothermic cooling. 

It is very interesting to notice that, starting in June 1886 at 44 0, 2, the bottom water 
required 149 days before any change of temperature occurred ; 79 days more raised the 



CLYDE SEA AREA. 85 

temperature (i.e. 228 clays of heating) to 46 o, ; and only 53 clays were necessary to 
carry it back to 45°'2. In 1887, starting from 44°*7 in May, 221 clays brought the 
bottom temperature to 46° "2, and 101 days more brought it back to 43° "8. 

Thus the rise of temperature at the bottom was at the average rate of o, 008 per clay 
in 1886 and 0°'007 in 1887 ; while the fall of temperature took place at the average rate 
of o- 015 per day in 1886 and o, 023 in 1887. The average rate of cooling at the 
bottom for the two years under consideration appears to be two and a half times as 
rapid as the average rate of heating ; in other words, the heat gained in five days is lost 
in two. 

The seasonal changes of temperature at Strachur are represented diagrammatically by 
the time-depth figure (fig. 8, Plate V.), which is on the same scale as that for Skate Island, 
with which it may profitably be compared. 

The most striking contrast between the two is the strongly-marked diagonal run of 
the isotherms in the Strachur diagram, and the fact that the penetration of heat was 
oreatest in 1887, while for Skate Island it was greatest in 1886. The retardation of the 
date of maximum temperature as the depth increases is beautifully brought out. 

In 1886 the surface was above 50° from July 1st to October 15th, and the isotherm 
of 50° only reached its maximum depth (23 fathoms) on October 1st. It thus took 92 
clays to carry this isotherm 23 fathoms clown, while at Skate Island 110 clays sufficed to 
carry it to 105 fathoms. 

In 1887 the surface was above 50° from May 24th to November 1st, and the 
temperature of 50° penetrated to its greatest depth (30 fathoms) on September 24th, 
thus requiring 123 clays to work down, while 37 days sufficed for its return to the surface. 
At Skate Island practically the same time was taken for the temperature of 50° to 
reach 64 fathoms, which was the maximum attained ; and early in August the 
temperature of 54° worked clown at both stations to the same small depth of 8 
fathoms. 

In 1888 the observations are complete enough to show that the surface was over 50° 
from July 24th to October 18th, while the maximum depth, reached by that temperature 
on August 24th, after 31 clays, was 12^ fathoms. 

The maximum temperature at the bottom, due to the summer's heat of 1886, was 
reached on February 24th, 1887, 194 days after the elate of the surface maximum, and 
54 clays after the succeeding surface minimum. The minimum at the bottom occurred on 
April 15th, 50 clays after the maximum. The summer's heat of the exceptional year 
1887 reached the bottom more rapidly, the maximum occurring there on December 31st, 
just 169 clays after the surface maximum, and 45 days before the surface minimum. 
The minimum at the bottom was on April 24th 114 days later than the maximum. 

In the Channel the bottom and surface maxima are simultaneous, in the Arran Basin 
at Skate Island the average of two years showed the bottom maximum to be retarded 
63 clays, while in Loch Fyne, at Strachur, the retardation averaged 182 days, or 
practically six months. This is a very striking illustration of the influence of increasing 



86 



DR HUGH ROBERT MILL ON THE 



isolation on thermal conditions, and shows how much the ready change of temperature 
in natural bodies of water depends on free circulation. 

Observations at Dunderaive. — At the observing station, Dunderawe Castle bore 
N. 21 cables, soundings being made in the centre of the loch at a depth of 35 fathoms. 
This was on the slope towards the head of the loch, about midway between the head and 
the relatively flat floor of the deepest part, the slope being much more gradual than 
that near Furnace at the other end. The observed density of the water was as 
follows : — 

Surface, 9 observations. 
Mean, ..... 1-01914 

Maximum, .... 1*02440 

Minimum, .... 1-00657 

Average percentage of sea-water, . . 70 - l 

In vertical section 90 - 2, or in normal year 89"8. 



Bottom, 9 observations. 

1-02450 

1-02479 

1-02412 

94-2 



Table XXXI. — Temperature Observations at Dunderaive. 



No. . . . 
Date . . . 
No. of Points 
Temp. 
Slope . . . 



1 

20.4.86 l 22.6.86 



9 
41-8 
+ 0-3 



9 
44-5 
+ 5-1 



3 

11.8.86 
10 

47-9 



4 
27.9.86 

7 
50-0 



+ 9-7 +7-3 



5 

17.11.86 

12 

49-0 

-1-9 



6* 
30.12.86 

15 
47-0 
-4-0 



7 
5.2.87 

6 
44-5 
-2-6 



29.3.87 

13 

45-0 

-0-9 



9 
10.5.87 

9 
.45-8 
+ 5-2 



10 

16.6.87 

14 

47-3 

+ 6-1 



11 

8.7.87 
12 
47-9 

+ 8-2 




13 14 

23.9.875.11.87 



8 
5M 
+ 4-8 



10 
49-8 
-1-1 



15 

7.11.87 

12 

49-6 

+ 0-6 



16 

17.12.87 

15 

47-0 

-4-7 



17 

14.2.8! 

12 

45-9 

-2-1 



18 

23.3.8* 

6 

43-2 

-0-4 



19 
2.6.88 

9 
45-3 

+ 2-4 



20 

24-8-88 

13 

49-2 

+ 9-7 



21 

25.8.88 

10 

49-3 

+ 10-1 



22 

17.10.8 

6 

49-0 

+ 2-3 



* West of Dunderawe. 

Curves of very slight slope, showing almost homothermic conditions, occurred three 
times — Nos, 1, 15, and 18. No. 15 will be specially alluded to, the others were both 
early spring curves at or near the minimum temperature of the year. 

Curves of great range are represented by ten positive and five negative cases, most 
of which arc somewhat irregular. Cases of well marked intermediate minimum in 
the positive curves occurred in No. 2 (June 1886), and of intermediate maximum in 
a negative curve in No. 5 (November 1886) and No. 17 (February 1888), the latter 
being a very well formed sickle shape. 

The main feature of the Dunderawe curves, like those for Inveraray and Strachur, is 
their great diversity of detail, showing compounds of the clearly recognisable types. 

The steepest gradients were 2 0, 8 and 2°*6 in successive single fathoms from to 2 



CLYDE SEA AREA. 87 

(No. 10); 9° in 1 fathom from 1 fathom to 2 fathoms (No. 11), — in this case the 
range of the fathom above and the fathom below were only 0°'4 each ; 8° "2 in 1 fathom 
(0-1 of No. 6), but here there was a change of 5° in 4 inches, the surface of the loch 
being frozen at the time, and the weather dead calm. Under the ice, at 2 inches depth, 
the temperature was 36°, and at 6 inches 41°, at 6 feet 44°. The other cases are 
2°"7 in 1 fathom from 1 to 2 fathoms (No. 14) ; 8°*8 in 4 fathoms, or an average of 
2° '2 per fathom in No. 21. All these are cases of rapid surface heating or cooling. 

An interesting case of possible erroneous deduction is shown in looking at the mean 
temperatures of the lowest 5 fathoms : — 

Nos. . .12 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 29 21 
Temperature 41-6 42-9 44-2 45-2 48-7 47"2 45-6 45-2 44-3 45-2 457 46-8 48*5 49-4 49-2 48-2 45-6 43-4 44-0 447 4:V9 477 

Date 27.9.86 17.11.86 30.12.86 5.2.87 29.3.87 10.5.87 16.6.87 8.7.87 

Here observations on Sept. 27th, 1886, March 29th and June 16th, 1887, gave exactly 
the same result ; and if no other observations had been taken it might reasonably be 
supposed that at the depth of 35 fathoms the temperature was constant, whereas these 
figures happened to be observed in course of successive stages of heating up, cooling 
down, and heating up again. Here the apparently impartial distribution of dates — 
autumn, spring, summer — would be apt to confirm a rash generalisation. The existence 
of constant temperature at the bottom in the case of Inveraray and Strachur would 
have been accepted as proved if three observations in 1886 and two in 1887 had been 
omitted. Frequent cases of such fallacy by coincidence have impressed on me the great 
caution necessary in uniting points by a curve. 

On November 5th and 7th, 1887, observations were made, on the former day in calm 
weather, on the latter day with a strong N.E. (down-loch) wind. Both were in the 
afternoon, when the tide was about the same phase. On November 5th the mean 
vertical temperature was 49°*8, on the 7th 49°'6. On the 5th (Curve 14) there was low 
surface temperature (45°"9), rising to 49°"8 at 5 fathoms, stationary at or above 50° from 
7 fathoms to 24 fathoms, then sinking to 49° '2. On the 7th (Curve 15) the temperature 
nowhere reached 50°. It was 49°'8 on the surface, 49°"9 at 10 fathoms, and then fell 
steadily to 49° "2. This showed thorough mixture of the water by the action of wind. 
The sounding on the 7th was about 1 fathom deeper than on the 5th, and thus the mean 
temperature of the latter was slightly reduced. There was practically no loss or gain of 
heat between the two occasions, the difference being merely a redistribution of tempera- 
ture by mixture. Curves 20 and 21 were observed on August 24th and 25th, 1888 
(see fig. 37 in Plate XXIX.). Both days show great range of temperature. On 
the 24th it fell from 57°'l on surface to 52°'9 at 5 fathoms; on the 25th from 
60°'8 to 52°. On the 24th it fell gradually to 51°'8 at 12 fathoms, sharply to 
48° at 22 fathoms, and with very exceptional abruptness to 45°"5 at 24 fathoms, 
then gradually to 44° - 3 at the bottom. On the 25th the fall was slightly irregular, 
but in the main steady from 52° at 5 fathoms to 45 0> 8 at bottom. The curves 
crossed twice at 4 fathoms and 23 fathoms. On the second occasion there was marked 



88 



DR HUGH ROBERT MILL ON THE 



warming of the 4 superficial fathoms, cooling by nearly f° of the next 19 fathoms, 
and great warming of tire lowest 10 fathoms. The mean temperature of the section was 
practically unchanged. The curves for both dates at Cuill were simply those of the 
upper 15 fathoms, the compensating action of the lower layers not there coming into play. 

Curve 9 (fig. 36, Plate XXIX.), a simple parabola showing spring heating from the 
surface temporarily arrested, is interesting when compared with the nearly homothermic 
curve for Furnace (fig. 28, Plate XXVIII.) at the same date. The whole question thus 
requires for its explanation a study of the vertical axial sections, many of the peculiarities 
of temperature change being due to the upward surge of deep, cold water, caused by dis- 
turbance of equilibrium by down-loch winds. This action is quite different at Dunderawe 
and Furnace, the difference being due to the closed end of the loch lying beyond 
Dunderawe, so that up-loch winds produce a banking-up and return-under-current of 
surface water, while at Furnace the effect of a down-loch wind is to drive surface water 
away to the Gortans Basin. 

Observations at Cuill. — This station, situated in mid-channel, near the head of 
Loch Fyne, has the farm-house of Cuill bearing N. by W. 1|- cables. The depth is 15 
fathoms. To the south-west the water deepens uniformly, to the north-east it shoals 
steadily, the station being on the upper part of the ascending slope at the head of the 
loch. 

The density of the water, as observed, is as follows : — 

Surface, 10 obsei'vations. Bottom, 9 observations. 

Mean, . . . 101435 ... 102427 

Maximum, . . . 102420 ... 102463 

Minimum, . . . 100114 ... 002359 

Average percentage of sea-water, 56"8 ... 93 - 4 

In vertical section 87 - 3, or for normal year 86'8. 







Table XXXII. — Temperature Observations at Cuill. 








No. ... 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


Date . . . 


20.4.86 


22.6.86 


11.8.86 


27.9.86 


17.11.86 


5.2.87 


29.3.87 


10.5.87 


16.6.87 


8.7.87 


15.8.87 


No. of Points 


7 


9 


12 


4 


9 


9 


5 


9 


9 


8 


7 


Temp. . . . 


417 


46-2 


51-1 


52-3 


48-7 


44-0 


44-4 


47-8 


49-5 


487 


53-1 


Sin],.' . . . 


o-o 


+ 5-1 


+ 7-4 


o-o 


-2-7 


-1-5 


-0-6 


+ 3-5 


+ 3-9 


+ 6-4 


+ 4-9 




12 


13 


14 


15 


16 


17 


18 


19 


20 


21 




Date . . . 


23.9.87 


5.11.87 


7.11-87 


17.12.87 


23.3.88 


2.6.88 


24.8.88 


25.8.88 


27.8.88 


17.10.88 




No. "f Points 


4 


6 


11 


12 


6 


3 


9 


6 


8 


6 




Ti mp. . . . 


53 1 


49-4 


49-6 


14-7 


43-2 


45-6 


52-8 


52-1 


53-7 


49-5 




Slope . . . 


+ 2*5 


-1-6 


+ 0-1 


-6-5 


-o-i 


+ 6-2 


+ 4-3 


+ 6-7 


+ 7-2 


+ 0-8 





CLYDE SEA AKEA. 89 

The curves, like those for shallow water in all parts of the Area, may be classed 
roughly into two groups, — the equinoctial occurring in spring and autumn, when homo- 
thermic conditions prevail, both being a straight line (the vernal occurring at the annual 
minimum, the autumnal somewhat after the annual maximum) ; and the solstitial, 
characterised by great slope, the summer (during the months of heating) being positive, 
the winter (during the months of cooling) being negative (see fig. 38, Plate XXIX.). 

The homothermic curves for this station are Nos. 1 (April), 4 (September), 14 
(November), 16 (February), 17 (June). No. 7 (March) very nearly conforms to the 
type. Of these No. 17 (June) is abnormal, occurring during rapid heating, and 
its homothermicity is due not to seasonal change, but to local and temporary mix- 
ture. 

Of the summer solstitial curves, the form was paraboloid on two occasions, — No. 10. 
which showed a steady diminution of the rate of fall of temperature from surface to 
bottom, and No. 12, which was not sufficiently defined to speak certainly of. No. 9 was 
nearly of the same form, but differed by a rapid fall at the bottom. Nos. 18 and 19 
also, except for flattening at the bottom, agree fairly with the type. No. 2 is a double 
parabolic curve, showing the division of the water into four zones, of rapid fall, nearly 
constant temperature, rapid fall, and nearty constant temperature. Nos. 8, 11, and 20 
are paraboloid, except for a layer of constant temperature on the surface, in two cases 
showing surface cooling and an intermediate maximum. In these cases the most rapid 
change of temperature with depth took place well below the surface, but in all other 
cases the surface layer showed most rapid change. The steepest superficial gradients 
were 5°"6 in the first fathom, 7° in 2 fathoms (3°'5 per fathom) in No. 18 (24.8.88); 
8°'6 in 3 fathoms (2 0> 9 per fathom) in No. 19 (25.8.88); 4°-2 in 1 fathom, or 8°'3 in 
3 fathoms in No. 9 (16.6.87) ; 3° "2 in 1 fathom, or 11° in 3 fathoms (3° 7 per fathom) in 
No. 10 (8.7.87) : 3° in 1 fathom (Nos. 3 and 20) is the maximum for those with a slight 
surface gradient. 

The negative solstitial curves show the paraboloid form of a rapidly cooling surface 
layer resting on a uniformly warm mass in Nos. 7 and 13 (March and November 
respectively). No. 15 (December) shows a nearly uniform rise from surface to bottom 
with intermediate pauses, maximum gradient 4° '4 in 1 fathom (from 1 fathom to 
2 fathoms). No. 5 is an interrupted paraboloid, showing fall of 6° "4 in 1 fathom (0 to 
1 fathom), and 3°'4 in 1 fathom (from 2 to 3 fathoms). No. 6 (February) is remarkable 
as being the minimum for the season, and shows a range of 4°*4. This range is com- 
pounded of 3° -4 fall in the first 3 fathoms, and 1° fall in lowest 5 fathoms. The inter- 
mediate zone of 9 fathoms had constant temperature ; as the whole mass might be 
expected to have at that season. Curves- 13 and 14, observed on November 5th and 7th, 
1887, are strikingly different. On the 5th it was calm, with average temperature 49° - 5, 
surface at 46°, bottom at 50°'l ; temperature of 49°-5 occurring at 4 fathoms. The 
7th was a day of strong north-east wind, blowing directly down the loch ; the mean 
temperature was 49°-6, the surface 49°7, the bottom 49°'5, and the temperature 

VOL. XXXVIII. PART I. (NO. 1.) M 



90 DR HUGH ROBERT MILL ON THE 

practically continuous between, a very striking case of complete mixture by wind 
without loss or gain of heat. 

Curves 18, 19, 20 were observed on 24th, 25th, and 27th August 1888. The obser- 
vations were all made in the afternoon, and in about the same state of tide. The wind 
was from a southerly quarter, very light on the 24th, fresh on the 25th, and strong on 
the 27th. It was practically an up-loch wind. On the 24th the mean temperature was 
52 0, 7, on the following day 52°. The surface temperature had meanwhile risen from 60°"8 
to 62°"3, the bottom temperature had fallen from 49°'4 to 47°'4. The depth was the same, 
15 fathoms. The curves crossed at 1\ fathoms, showing slight heating in the upper 
layers, and very marked and increasing cooling in the lower. The fall of 0°7 in mean 
temperature was thus the result of great incursions of cold water from beneath, while 
warm surface-water was flowing in above. This serves to suggest a double action on the 
part of the south wind as shown (fig. 39, Plate XXIX), similar to the double action 
noted in the case of the Gareloch cross-section. Between the 25th and 27th, 1°'6 of 
warmth was added. All above 2 fathoms was greatly cooled, all below it still more 
greatly heated, the same temperature occurring about 3 fathoms deeper throughout than on 
the 25th. This might indicate that the continuance of the up-loch wind had overcome 
the double action, and was now driving the warmer water to the greater depths, and 
drawing up some cooler water to the surface. Figure 40, Plate XXIX, shows a possible 
exjDlanation of this action. All above 1 fathom was cooler than on the 24th, so was all 
below 10 fathoms ; but between 1 and 10 fathoms there had been a great rise of tempera- 
ture. This matter will be treated more fully when considering the Temperature Sections. 

Temperature Sections of Loch Fyne. — A series of vertical sections along the axis of 
Loch Fyne were drawn with the vertical scale exaggerated 150 times as compared with 
the horizontal, in order to enable the isotherms of every degree Fahrenheit to be con- 
veniently represented. The section extends from Cuill to near Skate Island, in order 
to show the relation of Loch Fyne to the Arran Basin. From the 23 sections which 
have been drawn it is possible to obtain some insight into the thermal transactions of the 
water in Loch Fyne as a whole, and to calculate the mean temperature of the whole body 
of water at different times. They are reproduced in Plates XII. to XV. 

Section I, 20^ April 1886. — This shows the minimum and most uniformly 
distributed temperature of the entire series. Temperature varied but little from 42°, 
with a general seaward dip of isotherms ; 42° occurred deeper at Inveraray and Strachur 
than anywhere else in the section. The prevailing wind at the time of observation was 
a fresh breeze down-loch. In all cases the surface was slightly warmer than the depths. 

Section II, 2lst-22nd June 1886. — The prevailing wind was on the whole westerly, 
<>r nearly up-loch, and light, The arrangement of temperature was remarkable. The 
surface was about or over 48° everywhere, except at Otter, where there was marked 
upwelling of colder water. The isotherm of 45° preserved an average position of about 
10 fathoms, and the whole Gortans Basin was filled with water above 44°. The 



CLYDE SEA AREA. 91 

isotherm of 44° is represented as touching the Minard barrier, although there was no 
observation to fix it, and it may not have come so far down-loch. The line of 44° 
ran up the section to C.uill at about 12 or 15 fathoms. The temperature at all stations 
fell steadily to about 20 fathoms where the minimum occurred (at Strachur 42° - 3), thence 
the temperature rose much more slowly to the lower isotherm of 44°, which ran obliquely 
from near the lip of Minard Basin until it reached a depth of 50 fathoms at Inveraray. 
Beneath this was a gradual rise of temperature to 44°*1 or 44°"2. The upper layers were 
crowded with close parallel isotherms, showing surface heating. The lines of 44°, 43°, 
and 42° "5 formed a series of closed lenticular curves, near each other above and widely 
separated below, indicating a mass of isolated cool water entirely surrounded by warmer 
layers, and separated by the warmer Gortans Basin from water slightly below 44° at the 
same position (though without the intermediate minimum) in the Arran Basin. 

Were it not for Section I. we would naturally assume that the isolated cold mass 
represented the winter minimum slowly working its way down through the remnants of 
the undisturbed warmth of the previous summer, and pursued above by the rapidly 
increasing warmth of the next summer. But Section I. shows that the whole mass 
had started at about 41°"8, and that considerable heating had taken place throughout. 
Hence the problem is to account for the water below 20 fathoms heating up more 
rapidly than that between 15 fathoms and 10 fathoms. 

Many hypotheses were tested. The wind causing a rotary circulation either 
transversely or longitudinally might account for it, but there was no record of a pro- 
longed steady wind likely to produce such a result, and when wind of the kind demanded 
by this hypothesis occurred, it was not accompanied by similar conditions in the water. 
No satisfactory conclusion as to the origin of the distribution of temperature has been 
arrived at. 

The whole mass of water might be supposed to heat up gradually, most rapidly on 
the surface, until the mass from, say 15 fathoms downward, came to a temperature 
about 42° *5. Then tidal or wind action might be supposed to fill the Minard Basin with 
warm dense water at a temperature over 44°, and this crossing the Minard bar with the 
tide would, in consequence of its density, pour down the slope, warming the lower layers 
while the fresher upper stratum would be heated sufficiently to maintain it at a less 
density than the central cold area. This condition once established, would tend to persist. 
The density observations may be summarised as follows, the densities being given at 
the temperature of the water in situ. 



[Table. 



92 



DR HUGH ROBERT MILL ON THE 



Table XXXIII. — Density of Water in situ in Loch Fyne. 



1 Cuill. 


Dunderawe. 


Inveraray. 


Strachur. 


Furnace. 


Otter I. 


April 1886 ■ 


Surface . . 
Bottom . . 


1-02600 


1-02608 
626 


1-02576 


1-02605 
628 


1-02585 
652 


1-02574 
669 




r 

Surface . . 


478 


560 


562 


559 


580 


627 




5 Fathoms . 


564 




600 


579 


... 


643 


June 1886 ^ 


10 Fathoms . 
20 Fathoms . 
25 Fathoms . 


594 


618 


636 










Bottom 


623 


618 


638 


636 


649 


665 



The density of the water in Loch Fyne attained the actual maximum in June 1886, there 
being 2 per cent, more pure sea- water present than the average. However, April 1886 
was also a month of exceptional salinity, the amount of sea-water present in Loch Fyne 
then being 1'3 per cent, above the average. In April the difference between the density 
in situ of surface and bottom water, expressed in units of the fifth decimal place, 
was 18 at Dunderawe, 23 at Strachur, 66 at Furnace, and 95 at Otter. These 
differences corresponded to an increasing difference in salinity between surface and 
bottom water as the Arran Basin was approached, due to the greater salinity of the 
bottom water seaward, the surface salinity on this occasion being nearly the same along 
the whole length of the loch. It is difficult to understand in the light of Table XXXIII. 
how density would account for the continuance of the cold layer of intermediate water, 
because at Inveraray the salinity [i.e., density at 60° F.) of the water at 25 fathoms 
was r02465, and at the bottom 1*02486, a difference of 21, while the actual density 
in situ at 25 fathoms was in consequence of its low temperature, 1*02636, whilst 
that at the bottom was only 1*02638, and at the bottom at Strachur 1*02636, leading 
one to expect the formation of convection currents, or at any rate the rapid suppression 
of the intermediate minimum. The fact that a similar arrangement of temperature never 
occurred again, except to a very slight extent, which could be readily explained by local 
heating, points to some special circumstance in the Spring of 1886 as the cause. The 
surface salinity of the Loch Fyne stations was higher in June 1886 than on any 
subsequent occasion, and the same was true of Loch Strivanhead, while the Arran Basin 
was scarcely above its average, thus indicating the possibility of mixture with lower- 
layers, and hinting at vertical circulation through wind action. But any argument drawn 
from this difference is weakened by the fact that in April 1886 the contrast in salinity 
between Loch Fyne and the Arran Basin was much greater, the surface water of the 
Basin being then actually fresher than that of the loch. 



CLYDE SEA AREA. 93 

Section III., August 10th -11th, 1886. — The wind at the time of observation was 
light, and blew up the loch. Since June the Arran Basin had heated up to 53°"5 on the 
surface, and 45° on the bottom. The Minard Basin was filled with nearly uniformly 
warm water. The isotherms cross it nearly horizontally clown to the level of the bars, 
but below that level the Gortans Basin remains warmer than the water at the same 
depth either outside or inside; e.g., at 30 fathoms it is 48° in Arran Basin, 48°"3 in 
Gortans Basin, and 46° in the Upper Basin of Loch Fyne. 

At Otter the warm skin is broken by somewhat superficial upwelling. In the Upper 
Basin below 45-50 fathoms the temperature is the same as in June. The cold mass is 
much reduced in size, and the area under 44° is now only 20 fathoms thick at Inveraray, 
its maximum. Its minimum temperature is 43° "3 (?), and the line of minimum has sunk 
to 35 fathoms. The cold mass is in contact with the landward end of the loch, but does 
not reach so far as Furnace. This cold sheet has effectually prevented the penetration 
of heat to the water below. 

The upper isotherms below 10 fathoms show a strong down-loch dip, which is due, 
probably, not to shearing motion set up by wind, but to actual heating by the overflow 
of dense warm water from the Gortans Basin. That this is a very important factor is 
proved by density observations. From Furnace to Cuill, at about 5 fathoms, a number 
of isotherms run very close to each other, showing a thin layer of hot water resting 
abruptly upon the slowly warming, cooler layer below. 

Section IV., 27th-2Sth September 1886. — The superficial layer of 20 fathoms ranges 
from 51° to 52 0, 5, the mass approaching to homothermic conditions, and entirely filling 
the Gortans Basin, where the minimum on the bottom is 50° '7. Outside, at the same 
depth, it is 50°, and at the bottom over 47°. Inside it is 46°. There is a very slight 
rise of the isotherms at Otter. 

In the Upper Basin the non-conducting pad of cold water has been practically 
warmed away ; but the minimum temperature, still over 44°, docs not yet quite reach 
the bottom, so that the fall of temperature is not quite uniform from the surface. The 
isotherms, on the whole, are slightly curved, following the contour of the bottom, and 
between 50° and 47°, about 30 fathoms, they are most crowded, showing a great mass of 
warm water passing rapidly into a great mass of cold water. The position of this 
Sprungschicht, as it has been termed in German, is very characteristic just below the 
lip of the Minard barrier, suggesting that the inflow of warm water from the Gortans 
Basin spreads over but does not sink through the cold mass filling the Upper Basin. 

Section V., 16th-17th November 1886. — In this section cooling from the surface has 
set in strongly, and the isotherms show some very interesting relations. Outside, the 
temperature rises to 51°, about 15 fathoms, and remains practically constant, the water 
growing somewhat warmer toward the bottom. The Gortans Basin is filled with water 
of the same temperature, the isotherm of 50° falling to the Minard barrier. Inside, the 
surface temperature falls toward the head of the loch, but the water grows warmer from 
the surface to about 15 fathoms, where the maximum (about 50°) occurs, and then cools 



94 DR HUGH ROBERT MILL ON THE 

steadily to 44° '2 at the bottom. In this section we see last winter's cold still undis- 
sipated below, but separated from this winter's cold, which is coming in above, by the 
remains of the summer heat occupying an intermediate position, the freshness of the 
surface water effectually resisting the formation of convection currents. 

Section VI, 29th-30th December 1886. — Great and general cooling is shown here. 
Outside, the surface is at 46° - 6, the bottom at 47° "4, but just outside the Otter barrier a 
patch of bottom water above 48° occurs. As no observation was made at Kilfinan, the 
extent of this can only be guessed. 

From Gortans the isotherm of 46° runs almost straight to the head of the loch at a 
depth of 5 or 6 fathoms, the surface temperature falling below 36°, without, however, 
sensibly chilling the water below on account of surface freshness. Ice, resulting from 
the freezing of floating rain or thaw water from land, prevented an examination of the 
head of the loch on this occasion. The isotherm of 47° slopes up from Minard barrier 
until it comes close to 46° at Inveraray and beyond. A maximum line of about 47°'5 
runs along the loch at about 20 fathoms, and beneath that depth the temperature falls 
gradually to 44° "8 on the bottom. The isotherms, as a whole, converge toward Minard, 
and diverge widely toward the head. 

Section VII., £th-5th February 1887. — Outside, the temperature is somewhat irregular, 
varying between 44° and 45° from surface to bottom, and the Gortans Basin forms part 
of the Arran Basin so far as temperature is concerned. A slight upwelling of warmer 
water from beneath appears at Otter. Inside, the temperature increases from 43° or less 
on the surface pretty uniformly to 46°*5 at 45 fathoms, then diminishes very gradually 
to 45°*7 on the bottom. The isotherms generally follow the contour of the bed of the 
Basin, except for a slight rising of the upper isotherms at Inveraray. 

It is noticeable, not only in this, but in almost all the sections, that Gortans Basin 
is part of the Arran Basin, receiving its surface water, and that the special enclosed 
character of Loch Fyne begins at Minard. 

Section VIII, 29th March 1887. — Here a condition of remarkable uniformity 
prevails. Practically the total range is from 44° to 45°. The surface and bottom of the 
Upper Basin are at, or slightly above, 45°; the intermediate layers are nearly 44° "5 ; 
while the Gortans Basin and the Arran Basin contain water at, and colder than, 44° in the 
middle. 

Here surface heating seems to be just beginning, and a general equalisation of tem- 
perature has occurred similar to that of April 1886, although 2° warmer. 

Section IX., IQth May 1887. — The Gortans Basin is now filled with water of nearly 
uniform temperature, 46° on surface, 45° on bottom. Outside, it is 46°"3 on the surface, 
and sinks to an intermediate minimum slightly under 44°. Inside, the surface layers 
grow warmer toward the head in a remarkable way, the warming, though not spreading 
down the loch, extending to several fathoms in depth, and the temperature exceeding 
50° near Cuill. The isotherm of 45° runs pretty straight from Minard to Cuill at a 
depth of 20 fathoms. Below that the water cools to a minimum, about 44° at 40 



CLYDE SEA AREA. 95 

fathoms, and warms to 44° 7 at the bottom, but this intermediate minimum is much less 
marked than in the previous year. 

Section X., 15th~16th June 1887. — Continued heating has taken place, and in all parts 
of the section the water now falls gradually in temperature from surface to bottom, all 
trace of an intermediate minimum having vanished from the Upper Basin, the bottom 
water in which is, however, a little colder than in the Arran Basin. In the Upper Basin 
and in the Arran Basin the isotherms on the whole dip seaward, but in the Gortans Basin 
they dip landward. From Kilfinan to Gortans the disturbance due to the narrow Otter 
bar is apparent, strong upwelling taking place, while curiously enough there is no dis- 
turbance of the isotherms at the Minard passage. Indeed, here Furnace seems the true 
boundary of the Upper Basin, as the isotherm of 46° reaches the bottom there, and the 
water down to the bottom remains much over 46° all the way to Otter, beyond which it 
again sinks. Here at depths below 25 fathoms the Gortans Basin, extended to Furnace, 
separates two masses of water below 46° by a slice, the temperature of which is from 47° 
to 46°*8, and the line of 48° sinks deeper in this basin than anywhere else in the section, 
although the surface temperature above it is only 51° as compared with 57° and 58° 
beyond Strachur. This is unmistakably a result of the mixed water pouring in past 
Otter. 

Section XL, 7th-SthJuly 1887. — Here the conditions of Section X. are accentuated, 
except the upwelling at Otter, which is scarcely marked. 

The surface water at many points is over 60°, forming a very thin hot skin covering 
the characteristic distribution. In the Upper Basin the isotherm of 50° lies at the depth 
of about 5 fathoms, scarcely 1 fathom deeper than in June. The isotherm of 46° is only 
a fathom or two deeper than in June at Strachur and Inveraray, while at Furnace, 
Dunderawe, and Cuill its position is unchanged, but temperature exceeds 45° down to 
the bottom, thus showing a slight warming. The very slight effect of the high surface 
temperature is remarkable. Still more striking is the crowding downward of the 
isotherms at Furnace, and to a less extent at Otter, leaving the Gortans Basin filled with 
a huge wedge of water from 1° to 2° warmer than that at like depths outside and inside. 
The approach to horizontality of the Upper Basin isotherms below the level of the 
Furnace brow, and the rapid seaward dip of those above it, suggest the advance of a body 
of warm water and its mixing by lateral translation. As no observations were taken 
between Furnace and Minard the precise landfall of the isotherms is not known, and the 
character of X. and XL may be of much more common occurrence than appears in 
the earlier sections. 

Section XII., 15th-16th August 1887. — The surface has cooled down a few degrees, but 
the mass of the water has warmed notably. The isotherm of 50° has sunk to the bottom 
in the Gortans Basin and to 30 fathoms in the Arran Basin, while from Furnace it curves 
up toward Cuill. The upwelling at Otter is very slight. The isotherms are closely 
clustered in the surface zone of 7 fathoms (55° to 52°), then spread more uniformly, 
clustered again about 25 fathoms (50° to 47°), forming a Sprungschicht at Furnace and 



90 DR HUGH ROBERT MILL ON THE 

Strachur, and below that they are widely spaced. The bottom water of the Arran Basin 
is now 2° warmer than that in the Upper Basin of Loch Fyne. The drawing of the 
section between Minard and Furnace is conjectural, and probably incorrect. 

Section XIII., 23rd September 1887.— Surface temperature has changed but slightly 
since August, while all the lower isotherms have sunk in fair proportion, indicating a 
general warming of the lower layers. 50° has reached 60 fathoms at Skate Island and 
30 fathoms in the Upper Basin, while the whole Minard Basin is over 52°. The gathering 
in of isotherms at the bottom at Furnace is more marked than ever, the change from 51° 
to 48° being compressed into 2| fathoms compared with 15 fathoms at Inveraray and 
30 fathoms at Kilfinan. 

Here the pouring in of warm water of uniform temperature seems to take place 
directly over the cold uniformly-temperatured layer sheltered from mixture by the 
Furnace brow. 

Section XIV., 5th November 1887. — This is a partial section from Strachur to the 
head of the loch. Below 25 fathoms the water has warmed steadily since Section XIII. 
Above 25 fathoms it has cooled most rapidly on the surface, which is at 46°. The 
temperature rises rapidly to 50° at about 6 fathoms, then slowly for a fraction of a 
degree, cools down again to 50° at 23 fathoms, and 49° at 40 fathoms. An excellent 
example of winter cooling in calm weather, leading to the inclusion of an intermediate 
maximum. 

Section XV., 7th November 1887. — In the interval from XIV. a strong gale from 
north-east (down-loch) prevailed, and the contrast of conditions is singularly instructive. 
The isotherm of 49° still runs straight across at 40 fathoms, and below it the condition 
as regards temperature is absolutely unchanged. But above 40 fathoms every trace of 
thermal stratification has vanished. The temperature rises uniformly to 49° "8 at the 
surface. Thorough mixture has taken place down to, but not below, the level of the 
brow at Furnace. This indicates that below 40 fathoms the Upper Basin is extremely 
isolated, and that complicated circulation and complete mixture may occur in the upper 
layers without disturbing the depths. 

Section XVI, 10>th-l7th December 1887. — The bottom water has warmed up to a 
little over 46°; the surface water has greatly cooled down, especially toward the head of 
the loch, and there is a rise of temperature from the surface to 48° about 17 fathoms. 
Nearly constant temperature (a little higher) prevails to 44 fathoms, where it sinks to 48' 
again, and then falls uniformly to the bottom. Seaward of Furnace the surface tem- 
perature ranges from 46° to 47°, but up the loch it falls steadily to 38°*2 at Cuill. The 
isotherms of 48° in the Upper Basin show a tendency to define a lenticular mass of 
warmer water, conceivably the remains of the great mixing of November 7th. 

Section XVII, 14th February 1888. — Great changes have occurred since Section XVI. 
The surface of the Upper Basin has cooled down to 42° or less, rising rapidly to 46° at 5 
fathoms, reaching a slightly higher maximum about 10 fathoms, falling to 46° again at 
18 fathoms, and from that position to the bottom remaining nearly constant, falling only 



CLYDE SEA AREA. 97 

to 45 0, 3. The centre of this layer of maximum temperature being nearer the surface than 
that of Section XVI. , shows that it is not a result of continuously progressive cooling, but 
rather due to some more abrupt changes. The marked cooling down to the bottom indi- 
cates a once continuous cooling from the surface ; the intermediate thin zone of warmer 
water possibly is all that remains of a surface heating due to warm weather, which, with 
the recurrence of cold, was capped by a chilled layer. The range of temperature in 
Gortans Basin and seaward is too slight to be discussed. 

Section XVIII., 22nd-2Srd March 1888. — A return to the nearly uniform conditions 
of the minimum is shown here. The temperature varies from something under 43° on the 
surface to something over 44° on the bottom. There are traces of a slight intermediate 
minimum in Gortans Basin, and the accumulation of warmer water on the bottom of the 
Arran Basin between Otter and Kilfinan is marked, as on several occasions of the approach 
to minimal conditions. 

Section XIX., 2nd-Ath June 1888. — Cooling has continued at the bottom, where the 
temperature in the Upper Basin is now 43° "3, but rapid heating has gone on from above 
downward without the formation of any trace of an intermediate minimum. The section 
is largely hypothetical, as no observations were made at Furnace, Minard, or Otter. 

Sections XX. and XXI. (Partial Sections), 2ith-25th August 1888 ; XXII, 
27th August 1888. — On the 24th there was a rapid fall from 60° on surface to 54° at 1\ 
fathom, a gentle fall (50° at 15 fathoms) to 48° at 22 fathoms, rapid fall to 46° at 23|- 
fathoms, and finally a gentle fall to 44° at 35 fathoms. 

On the 25th the surface temperature was somewhat higher, and the fall of temperature 
at the greater depths much more uniform, the crowded isotherms 48°-46° being in par- 
ticular well spread out. The range of temperature was remarkable. 

On the 27th the downward propagation of warmth was very clearly marked ; and the 
surface layers having cooled somewhat, an intermediate maximum was formed at about 3 
fathoms at the head of the loch. 

Section XXIII, 16th, 17th, 18th, and 19th October 1888.— This section was compiled 
from observations scattered over too long a time to be of much value. It appears to show 
the characteristic signs of a flow of warm water from the Gortans Basin over Furnace 
brow into the Upper Basin. The upper strata of water are assuming the homothermic 
form common in autumnal coolino-. 

The difference between the thermal changes in the Arran Basin and Loch Fyne is 
mainly due to the restricted entrance and the much steeper slope within the sill preventing 
the free mixture of the water from outside, and also to the low salinity of the surface 
water in the upper reaches. The resemblance of the Channel and Plateau to the 
Gortans Basin is very strong. The up welling at Otter keeps the Gortans Basin supplied 
with nearly homothermic water of much greater salinity than that found at the same 
depth in the Upper Basin, but on account of the steep slope beyond Furnace this water 
appears to spread over the cold layers of Loch Fyne, instead of following the ground and 

VOL. XXXVIII. PART I. (NO. 1.) N 



its 



DR HUGH ROBERT MILL ON THE 



gradually mixing with the mass down to the bottom. There is, indeed, a certain amount 
of mixture, as is proved by the variations in the salinity of the deep water. How far 
this is due to tidal action we cannot say. Wind is certainly a more powerful agent for 
settiug up vertical currents in the water than tide is, but a steady wind in one direction 
rarely lasts long enough to produce its full effect. The tides, on the other hand, act 
continuously, and I have by further consideration been led to modify the opinion stated 
in Part II. p. 706, that tidal influence was insignificant as leading to the formation of 
deep currents in the Upper Basin. I do not find in the temperature observations enough 
data to found an exact theory upon, and the precise share of steady tidal action and 
spasmodic wind-action in stirring the depths of the Upper Basin must remain for the 
present undetermined. 

Table XXXIV. shows that even with constant temperature there is not stagnation 
at the bottom. 

Table XXXIV. — Bottom Salinity and Temperature. — Strachur. 





April 

1886. 


June Aus;. 
1886. 1886. 


Sept. Nov. 
1886. | 1886. 


Dec. 

1886. 


Feb. 
1887. 


March 
1887. 


May 

1887. 


June 
1887. 


July 

1887. 


Sept. 
1887. 


Average. 


Density at 
60° F. 

Temperature 
in situ. 


1-02450 
41-9 


1-02481 

44-1 


1-02517 
44-2 


1-02483 
44-1 


1-02422 
44-2 


1-02172 
44-7 


1-02441 
45-9 


1-02430 
45-5 


1-02447 
44-7 


1-02477 
45-2 


1-02479 
45-2 


1-02472 
45-3 


1-02465 
44-6 



Here we see that there were variations in the bottom salinity from its minimum to its 
maximum value during the period of constant bottom temperature, June to November 
188G ; and this fact shows that the exchange of water with the outside must have been 
very uniform and gentle indeed. The intermediate belt of minimum temperature would 
provide in June and August a means of chilling the warm dense Gortans Basin water as 
it sank, so that it would not carry its original temperature down with it, but between 
September and November no such explanation offers. The period June to September 
1887, when the temperature was constant, was also characterised by uniform salinity, 
and, but for the contradiction of the previous year, would have justified a presumption 
that constant bottom temperature indicated stagnation. 

Seasonal Variations of Temperature in the Mass of Water in Loch Fyne. — From 
the temperature sections the mean temperature of the whole mass of water in Loch 
Fyne from Otter to the head was calculated for each trip in the manner already 
explained (p. 10). The temperature of each layer of 10 fathoms was estimated by 
measuring the areas between successive isotherms, and the resulting figures were 
" weighted " by multiplying each with a factor representing the relative volume of the 
layers, and dividing the sum of the products by the sum of the factors. The factors in 
the case of Loch Fyne were : — 

Layer in fathoms, 0-10 10-20 20-30 30-40 40-50 50-60 Over 60 
Factor, . . 15'5 133 95 4-9 3*0 21 10 



CLYDE SEA AREA. 



99 



And if the mean temperatures for the several layers were a, b, c . 
temperature (T) of the whole mass is given by 

15-5a+13-3&+9-5c+4-9e&+3-Oe+2-l/+0. 



the weighted mean 



T = 



493 



Table XXXV. — Mean Temperature at various depths in Loch Fyne. 







Days 


Mean 




Mean Temperature 


of Layers. 




Section. 


Date. 


since last 


Temp. 
























Over 
60 






Trip. 


Weighted. 


0-10 


10-20 20-30 

1 


30-40 


40-50 


50-60 


I. . 


20.4.86 




42-06 


42-52 


42-00 


41-88 


41-76 


41-63 


41-56 


41-50 


II. 




21.6.86 


62 


44-43 


46-25 


43-56 


43-40 


43-56 


43-90 


44-05 


44-10 


III. 




10.8.86 


50 


47-94 


51-18 


48-25 


46-45 


44-54 


44-01 


44-12 


44-18 


IV. 




27.9.86 


48 


49-85 


52-18 


51-40 


49-27 


46-19 


44-70 


44-13 


44 00 


V. 




16.11.86 


50 


49-02 


48-84 


49-91 


49-81 


49-71 


46-58 


45-15 


44-50 


VI. 




29.12.86 


43 


46-44 


45-46 


47-04 


47-19 


47-05 


46-44 


45-60 


45-05 


VII. 




4.2.87 


37 


44-74 


43-73 


44-58 


45-00 


45-97 


46-40 


46-19 


46-04 


VIII. 




29.3.87 


53 


44-40 


44-47 


44-30 


44-31 


44-36 


44-54 


44-60 


44-80 


IX. 




10.5.87 


42 


45-35 


46-52 


45-24 


44-67 


44-30 


44-40 


44-59 


44-68 


X. 




15.6.87 


36 


47-74 


50-GO 


47-69 


46-77 


46-00 


45-12 


44-93 


44-80 


XI. 




7.7.87 


22 


48-81 


51-78 


48-44 


47-80 


46-67 


45-43 


45-30 


45-20 


XII. 




15.8.87 


39 


50-29 


53-30 


50-75 


49-31 


47-16 


45-98 


45-56 


45-15 


XIII. 




23.9.87 


39 


51-42 


53-22 


52-30 


51-63 


49-28 


46-89 


46 00 


45-40 


XIV. 




16.12.87 


84 


47-23 


46-00 


47-56 


48-03 


48-12 


48-00 


47-55 


47-00 


XV. 




14.2.88 


60 


45-37 


45-02 


45-68 


45-52 


45-37 


45-40 


45-35 


45-30 


XVI. 




22.3.88 


36 


43-33 


43-10 


43-18 


43-37 


43-65 


43-90 


44-00 


44-00 


XVII. 




2.6,88 


73 


45-36 


46-22 


45-47 


44-68 


43-95 


43-60 


43-40 


43-30 


XVIII. 






16.9.88 


106 


48-71 


49-83 


49-64 


48-79 


47-31 


45-40 


44-80 


43-50 



Table XX XV. gives for each of the eighteen complete sections the date, number of clays 
elapsing since previous trip, the weighted mean temperature of the mass of water, and 
the actual mean temperature of the seven ten-fathom layers. A selection of these 
figures is represented graphically in the curve, fig. 41, Plate XXX. On this curve also the 
mean temperature of the air at Callton Mor is given as an indication of the actual air- 
temperature over Loch Fyne. The air-temperature has the greatest range and is the 
earliest in phase ; the surface layer of 5 fathoms follows the air-temperature with a much 
diminished range, its maximum occurring 45 days later in 1886, and about 50 days 
later in 1887. The minimum is not easily compared, as the air-temperature on both 
occasions showed a double minimum three months apart, the surface-water minimum 
occurring between the two in 1887, and coincidently with the later air-minimum in 
1888. The water at 35 fathoms deep (mean of the layer 30 to 40 fathoms) had a less 
range, and its maximum was retarded 126 days after the air-maximum in 1886 and 
about 120 days in 1887. The minimum was 75 days later than that of the surface 
water in 1887, but synchronised with it in 1888. The bottom layer of 10 fathoms 
showed a very small range. The maximum was retarded 212 days after the air- 



100 DR HUGH ROBERT MILL ON THE 

maximum in 1886, and 185 days in 1887. The minimum similarly occurred about six 
months later than the minimum on the surface. The curves show considerable 
irregularity, particularly the bottom curve, for successive years ; but the general facts of 
retardation of phase and reduction of range with depth are clearly brought out. The re- 
tardation of the annual maximum with depth is expressed graphically in fig. 42, Plate XXX, 
where depths are ordinates, and the time, in days after the occurrence of the maximum 
annual temperature at 5 fathoms, are abscissas. In 1886 the bottom was 120 days behind 
the surface layer, in 1887 only 95 days. In 1886 the phase was simultaneous at 5 and 15 
fathoms, in 1887 tliirt}^ days were required for the maximum to sink to the latter depth. 
But in 1887 ten days more saw the maximum at 25 fathoms, while in 1886 twenty days 
were necessary. From 35 to 45 fathoms the descent of the maximum was at the same 
rate in both years, and 14 days more brought it to the bottom in 1887, while 48 days 
were necessary in 1886. The curves at all depths are, as in all cases, widely spread in 
heating up, and drawn much closer together while cooling down. The approximation is 
more apparent for curves of middle and bottom temperature, the surface remaining 
markedly higher during heating and lower during cooling, probably on account of the 
much lower salinity of the surface layer. The variations of the temperature of the 
water of the loch as a whole are much more regular than those of the separate layers, 
and admit of comparison with those of the Channel and Arran Basin, with which they 
are compared in Table LXIV. in the General Summary. 

Starting from a minimum of 42°, say on April 15th, 1886, the mass of water came 
to its maximum of 49° - 9 on September 30th, a gain of 7°"9 in 168 days, or an average 
of 0°"047 per day. This time of heating is practically the same as that for the Arran 
Basin, but the rise of temperature was 1°*7 less, or 5°*1 less than was gained by 
the Channel water, starting from the same minimum in 20 days less time. The daily 
gain was one-fifth less than in the Arran Basin, and practically only one-half of that in 
the Channel. The minimum (probably 43°"8) was reached on March 5th, 1887, 
showing a total loss of 6°'l in 156 days, or of 0°*039 per day on the average. Here 
also the period of cooling was practically the same as that in the Arran Basin, although 
the minimum was slightly higher, and the daily fall of temperature one-quarter less. 
The next maximum occurred on September 27th, 1887, when the temperature was 51 0, 5, 
showing a gain of 7°7 in 206 days, at the rate of 0°-037 per day. Here the rate of 
heating bore the same relation as before to that in the Channel and Arran Basin, but 
the period of heating was proportionally longer. A minimum of 43° "2 on March 30th 
showed the loss of 8°"3 in 184 days, or o, 045 per day. This rate of cooling was almost 
as rapid as in the Arran Basin, and its duration 15 days less. The last maximum 
observed (48° # 7 on September 15th, 1888) showed a gain of 5°*5 in 170 days, or at the 
rate of o, 033 per day. The mean duration of heating in Loch Fyne for the three years 
observed was 180 days, and for cooling in the two years 170 days. For the two years in 
which the observations for the three years are comparable the ratio of the period of 
heating to that of cooling was 100 : 115 in the Channel, 100 : 100 in the Arran Basin 



CLYDE SEA AREA. 



101 



and 100 : 91 in Loch Fyne. Thus it appears that increasing isolation tends to increase 
the period of gain of heat by retarding the date of maximum and reducing the rate of 
gain of temperature. 

The rate of heating at various depths, and for the mass of water as a whole, is given 
in Table XXXVL, and represented graphically in fig. 5, Plate IV. This shows that 
the mean rate of heating per day is greater than that of cooling in the upper half of the 
water, but less than the rate of cooling in the lower half. It also shows that the rate of 
change of temperature is on the average 0° - 040 per day for the whole mass of water, 
corresponding to 1° in 25 days. For the surface layer of 10 fathoms it is 0°'053, or 1° in 
19 days (maximum, May to August, 1° in 10 days heating, and October to December, 
1° in 12 days cooling) ; half way down it is 0°"033 per day, or 1° in 30 days ; and at the 
bottom only o, 015 per day, or 1° in 66 clays. Plotting these figures — the average daily 
change of temperature for the whole period — as absciss£e, with depths as ordinates, we see 
in fig. 43, Plate XXX., how the restriction of thermal change goes on increasingly 
until 40. 

Table XXXVL — Average Change of Temperature per diem in Loch Fyne. 









Change of 


Temperature in Degrees per Day. 




Dates. 


No. of 
Days. 


















Mass. 


0-10 


10-20 


20-30 


30-40 


40-50 


50-60 


Over 60 






Fathoms. 


Fathoms. 


Fathoms. 


Fathoms. 


Fathoms. 


Fathoms. 


Fathoms. 


21.6.86 


62 


+ 0-038 


+ 0-060 


+ 0-025 


+ 0-024 


+ 0-029 


+ 0-037 


+ 0-040 


+ 0-042 


10.8.86 


50 


+ 0-070 


+ 0-099 


+ 0-094 


+ 0-061 


+ 0-020 


+ 0-002 


+ 0-001 


+ 0-002 


27.9.86 


48 


+ 0-040 


+ 0-021 


+ 0-066 


+ 0-059 


+ 0-034 


+ 0-014 


0000 


- 0-004 


16.11.86 


50 


-0-017 


-0-067 


- 0-030 


+ 0-011 


+ 0-070 


+ 0-038 


+ 0-020 


+ 0-010 


29.12.86 


43 


-0-060 


-0-079 


-0-067 


-0-061 


-0-062 


- 0-003 


+ 0-010 


+ 0-013 


4.2,87 


37 


-0-046 


-0-047 


-0-067 


- 0-059 


-0-029 


o-ooo 


+ 0-016 


+ 0-027 


29.3.87 


53 


-0-006 


+ 0-014 


- 0-005 


-0-013 


-0-030 


-0-035 


-0-030 


-0-023 


10.5.87 


42 


+ 0023 


+ 0-049 


+ 0-022 


+ 0-009 


- o-ooi 


- 0-003 


o-ooo 


-0-002 


15.6.87 


36 


+ 0-066 


+ 0-097 


+ 0-068 


+ 0-058 


+ 0-047 


+ 0-020 


+ 0-009 


+ 0-003 


7.7.87 


22 


+ 0-049 


+ 0-081 


+ 0-034 


+ 0-047 


+ 0-030 


+ 0-014 


+ 0-017 


+ 0-018 


15.8.87 


39 


+ 0-038 


+ 0-039 


+ 0-059 


+ 0039 


+ 0-013 


+ 0-014 


+ 0-006 


o-ooo 


23.9.87 


39 


+ 0-029 


-0-002 


+ 0-040 


+ 0-059 


+ 0-054 


+ 0-023 


+ 0011 


+ 0-006 


16.12.87 


84 


-0-050 


-0-086 


-0056 


-0043 


-0-014 


+ 0-013 


+ 0-018 


+ 0-019 


14.2.88 


60 


-0-031 


-0-016 


-0-031 


-0-042 


- 0-046 


- 0-043 


-0-036 


-0-028 


22.3.88 


36 


-0-057 


-0-054 


-0-069 


-0-060 


- 0-048 


-0-042 


- 0-037 


-0-036 


2.6.88 


73 


+ 0-028 


+ 0-043 


+ 0-031 


+ 0-018 


+ 0-004 


- 0-004 


-0-008 


-0-010 


Mean Heatiri| 


y 


+ 0-042 


+ 0-056 


+ 0-049 


+ 0-038 


+ 0-033 


+ 0-019 


+ 0-015 


+ 0-015 


No. of Ca 


ses . 


9 


9 


9 


10 


9 


9 


10 


9 


Mean Cooling 


3 


- 0-038 


- 0-050 


- 0-046 


-0-046 


- 0-033 


- 0-022 


-0-028 


-0-017 


No. of Ca 


ses . 


7 


7 


7 


6 


7 


6 


4 


6 


Mean Change 




0-040 


0-053 


0-048 


0-041 


0-033 


0-019 


0-016 


0-015 



102 DR HUGH ROBERT MILL ON THE 

fathoms, where the mean daily change is only half that at the surface, and then the rate 
of change diminishes, until at 70 fathoms it is rather less than one-third as great as at 
the surface, and appears to approach a limiting value. This curve appears to indicate 
that no increase of the depth of Loch Fyne would suffice to absolutely prevent the 
influence of surface change of temperature from affecting the deepest water. It furnishes 
another proof of the necessity of caution in generalising from incomplete results ; for if 
observations had only been carried to 50 fathoms, it would have appeared probable that 
before 60 fathoms constant temperature would be reached. 

As in the Arran Basin, the air- temperature curve for Loch Fyne cut the surface 
curve at the maximum, and the mean curve rather after the maximum. The theoretical 
reason of this coincidence is obvious. The surface water continues slowly to rise in 
temperature while the air is cooling down, as long as the actual temperature of the air 
is above that of the surface, but as soon as the cooling air reaches the same temperature 
as the water this rise ceases, and as the air becomes colder it chills the surface layers by 
contact, and causes the first fall of surface temperature. On the other hand, the cooling 
of the water appears to be checked at the minimum by the heating power of the sun, and 
the air does not become warmer than the water until the latter has begun slowly to heat 
up. As in the curves for the Arran Basin, the surface-water temperature in rising is, 
after the air-curve crosses it, almost the exact mean between the air-temperature and that 
of the mass of water. 

During the rise of temperature the air was warmer than the surface water for 165 
days in 1886, 120 days in 1887, and 150 days in 1888, an average of 145 days; and 
during the rest of the time the air was colder than the surface water for 216 days in 
1886-87, and for 222 days in 1887-88, an average of 219 days. Speaking roughly, we 
may say that the air is warmer than the surface water for four and a half months, from 
the beginning of May to the middle of September, and colder for the seven and a half 
months from the middle of September to the end of April. The number of days when 
air was warmer than water for the two seasons 1886-88 were, for the Channel, Arran 
Basin, and Loch Fyne respectively, 134, 136, and 143; while for air colder than water 
they were 237, 228, and 219. This effect of isolation in lengthening the period in which 
the air is warmer is evidently due to the lower maximum resulting from a slower rate of 
rise of temperature, giving a longer interval before the falling air-temperature reaches 
the same value and stops further rise of temperature. 

By interpolating probable values for the first three months of 1886, it is possible 
to compare the annual mean temperatures of the two years ; and by interpolating probable 
values for the last three months of 1888, the hypothetical annual means for three }^ears 
may be compared. 

Hence each year the surface water was warmer on the average than the air, so that 
it exercised, on the whole, a warming influence on the atmosphere, while the mass of 
water, as a whole, was very little warmer than the air, and in 1888 appeared to be a 
little colder. In 1886 the excesses of temperature of the surface water over the air in 



CLYDE SEA AREA. 



103 



the Channel, Arran Basin, and Loch Fyne were respectively 1°7, 1°"2, l° - 3 ; and in 
1887, 1°7, 2 0, 3, 1°*7 ; or on the average of the two years, l°-7, 1 0, 7, 1 0, 5. The figures 
for the Arran Basin are probably the least trustworthy ; but it appears that the isolation 
of Loch Fyne has practically no effect on the relation between the temperature of the 
lower strata of the air and the upper strata of the water. The difference produced by 

Table XXXVII. — Mean Annual Temperatures of Air and Water for Loch Fyne. 



Year. 


I. Air (mean 
for Area). 


II. Air 

(Calltou Mor.). 


III. Water. 
Surface 5 
fathoms. 


IV. Water. 

Mass. 


Difference 
Air II. and 
Water III. 


between 
Air II. and 
Water IV. 


1886 
1887 
1888 
Mean. 


46-2 
47-0 
46-7 
46-63 


45-5 
46-9 
46-6 
46-33 


46-8 
48-6 
47-1 
47-50 


45-8 
47-o 
46-0 
46-43 


-i-3 
-i'7 

-o-5 

-ri 7 


-°"3 
-o-6 
+ o-6 

- O'lO 



isolation comes out on comparing the excess of warmth of the mass of water in each 
division over that of the air. On the average of 1886 and 1887, this factor for the 
Channel, Arran Basin, and Loch Fyne was l° - 7, 0°"35, o, 45. Here the great depth of 
the Arran Basin, and the uncertainty as to the true air and water mean temperatures, 
prevent us from accepting its figure as of equal value with the other two. 



The Gareloch. 

This division is defined as the area lying north and west of Eow Point. It is five 
miles long, and less than one mile wide at the widest. Outside Row Point a wide and 
comparatively shallow basin communicates directly with the Estuary. The tides run 
strongly into and out of the loch. The configuration of the loch is described in Part I. 
p. 646, and sections given in No. 17, Plate 9 of that instalment. The area is 4'23 
square miles, with a land drainage of 12*40 square miles. The ratio of water to total 
drainage-area is 1: 3*93, and is the largest ratio of any of the lochs. 

The Gareloch is characteristically shallow and flat-floored, with gently sloping banks, 
forming a single basin with a clearly defined bar. Its mean axial depth is 18 fathoms, 
and its average depth only 7 fathoms. The tidal rise is 9 feet. 

In the Gareloch the average percentage of pure sea-water was found to be 89*6 per 
cent, by volume. It is the freshest of the divisions of the Area, and is situated in a land- 
ward position, exposed to a considerable range of climatic conditions. It may be con- 
sidered in this place as a fourth and distinct type, showing temperature changes quite 
different from those of the Channel, Arran Basin, or Loch Fyne. 

Observations at Row I. — This station is situated outside the Gareloch, with Row 



104 



DR HUGH ROBERT MILL ON THE 



Beacon bearing N. one-sixth mile. The depth is 12 fathoms, in an isolated patch 
shoaling inward to a shallow bar, and more gently seaward to a plateau of the minimum 
depth of 8 fathoms, beyond which a tongue of deeper water leads westward to Dunoon 
Basin, while it shoals eastward into the estuary. The average density of the water was : — 



Mean (7 observations) 

Maximum 

Minimum 



Surface. 

1-02223 
102387 
101985 



Bottom. 

1-02407 
1-02477 
1-023G7 



The average percentage of pure salt water at "Row" was 8 5 "7 at surface, 91 "3 at 
bottom, or 90 "4 in vertical section, and it may be assumed for an ordinary year as 90 "1. 



Table XXXVIII. — Temperature Observations at Bow I. 



No. . . . 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 


14 


Date . . 


13.4.86 


16.6.86 


4.8.86 


24.9.86 


11.11.86 


28.12.86 


25.3.87 


6.5.87 


13.6.87 


6.8.87 


29.11.87 


9.2.88 


28.3.88 


6.9.88 


No. of Pts. 


3 


3 


4 


4 


4 


6 


7 


2 


3 


8 


6 


6 


3 


6 


Temp. . . 


42 3 


48-7 


51-6 


53-1 


50-2 


44-0 


43-0 


46-1 


51-0 


55-8 


477 


44-5 


41-8 


537 


Slope . . 


+ 1-0 


+0-4 


+0-3 


+ 0-1 


-1-1 


-0-8 


-0-2 


+ 0-9 


+0-6 


+1-6 


-1-0 


-0-5 


-0-1 


+ 1-0 



The curves which were drawn from the observations were uniform in all cases except 
No. 14, where the temperatures at surface, 5 fathoms, and bottom were 41°"9, 41°*6, and 
42 0, 2, showing an intermediate minimum ; but as only three points were determined, this 
may be neglected. Nos, 1, 2, 3, 4 showed a successive reduction of positive slope ; No. 4, 
the maximum for the year, being practically homothermic ; Nos. 5 and 6 — the cooling 
curves — were of greater range relatively, showing a marked negative slope ; but No. 7 
was again almost homothermic, this time at the minimum. Nos. 8, 9, 10 had increasing- 
positive slope as warming continued, No. 10 — the maximum — showing a range of 3° in 10 
fathoms; Nos. 11 and 12 showed diminishing negative slope; and No. 13 is again a 
homothermic minimum. 

The greatest range between surface and bottom temperatures was 4°*8, on 29th 
November 1887, in 11 fathoms, the bottom being warmer; 3° of the change took place 
in the first fathom. The effect was that naturally due to rapid surface-cooling. The 
comparatively small vertical range in the curves, as a whole, is readily accounted for by 
tidal mixture. 

The maximum temperature of the mass of water was 55°'8 in August 1887, and the 
minimum 41 0, 8 in March 1888. Of the 15 soundings, 9 were made in the summer and 
6 in the winter half-year, the water warming in the former, and cooling in the latter 
season. The period of observation included three minima (in March or April) and three 
maxima (in August or September). 

Observations at Row II — The observations were made just inside the Gareloch, Row 



CLYDE SEA AREA. 



105 



Beacon bearing S. ^ mile. The depth was 23 fathoms, the fall from the bar at the 
mouth of the loch off Eow Point being very abrupt to this point, but the loch then remains 
almost of the same depth, forming a single trough all the way to the head. The average 
density of surface water from four observations was 1*02254, maximum 1*02387, and 
minimum 1*01985 ; and on the bottom the mean from five observations was 1*02341, 
with a maximum of 1*02380, and a minimum of 1*02239. 

The surface water is practically identical in salinity with that of Row I., but the 
bottom water is considerably fresher, as might be expected. 



Table XXXIX. — Temperature Observations at Roiv II. 



No. . . . 


1 


2 


3 


4* 


5 


6 


7 


8 


9 


10 


11 


12 


13 


14 


15 


16 


Date . . 


13.4.86 


16.6.86 


4.8.86 


11.11.86 


28.12.86 


2.2.87 


25.3.87 


6.5.87 


13.6.87 


6.8.87 


30.9.87 


29.11.87 


9.2.88 


28.3.88 


7.6.88 


6.9.88 


No. ofPts. 


5 


4 


7 


4 


6 


6 


3 


4 


3 


6 


4 


3 


6 


3 


6 


3 


Temp. . . 


41-8 


48-3 


52-6 


49-4 


44-4 


42-9 


42-9 


45-9 


50-6 


57-6 


53-9 


46-6 


44-0 


41-9 


46-3 


54-1 


Slope . . 


+ 1-6 


+ 1-0 


+ 0-6 




-1-3 


-1-0 1 o-o 


+ 0-9 


+ 1-0 


+0-4 


-0-1 


-1-8 


-0-3 


-o-i 


+ 1-3 


+ 1-3 



* To 10 fathoms only. 

Three observations, those of December 1886, February 1887, and February li 
show mixed slopes indicating the existence of intermediate layers at different tempera- 
tures. Nos. 1, 2, and 3 showed positive slope with diminishing range, the greatest 
range of the whole series being No. 1 of 2°*7 ; at surface, 44°*1 ; at bottom, 41°*4 ; and 
of this there was a range of 2° in the first 4 fathoms. The small maximum range of 
2°*7 in 20 fathoms is a distinct feature of this set of curves. 

In order to determine the relation to season of the positive and negative slopes, a curve 
(fig. 44, Plate XXX.) was constructed, showing positive slope by the difference (drawn 
above mean line) between the warmer upper 5 fathoms and cooler lowest 5 fathoms ; 
and negative slope by the difference between the colder upper 5 fathoms and warmer 
lower 5 fathoms. 

Fig. 44 shows the seasonal change of slope for both Row II. and Shandon. At both 
stations the curve of slope cuts the zero line about the equinoxes, showing that as long 
as the period of daylight is greater than that of darkness, the surface water as a whole 
is warmer than that beneath ; but when the period of darkness exceeds that of daylight, 
the surface water becomes colder than that below. The period of greatest negative slope 
appears to occur in December about the time of the winter solstice. In 1886 the maximum 
positive slope occurred nearly at the summer solstice, but in both the other years it was 
delayed until the month of August, showing that the surface water continued to gain heat 
rapidly for two months after the summer solstice. The curve cut the zero line in 
ascending at or before the annual minimum of temperature, and cut it in descending at 
or after the annual maximum. 

The curve of seasonal change of mean temperature ran on the whole parallel to that 

VOL. XXXVIII. PART I. (NO. 1). O 



100 



DR HUGH ROBERT MILL ON THE 



of Row 1. (q.v.) and included three minima and three maxima, but unfortunately neither 
maxima nor minima were fully mapped out by observations. The mean temperature was 
throughout somewhat lower than that of Row I. The mean of the 1 6 average vertical 
temperatures was 47°7, or o, 4 lower than for Row I. Of the 1G soundings, 9 were in the 
summer and 7 in the winter half-year. Omitting two soundings which were not repre- 
sented at Row L, the mean for Row II. comes out as 47°"6, or 0°*5 lower than that for 
Row I., it being thus apparent that the station inside the barrier was distinctty colder 
than that outside, largely of course on account of the much greater depth. 

The strong tidal stream running into and out of the narrow and shallow mouth of 
the Gareloch produces a distinct effect in mixing the water vertically, and when a 
breeze is blowing against the tide, the commotion produced is very considerable. 

No special observations were made as to temperature, but the appearances were 
exactly similar to those at Otter Spit (see Loch Fyne), which were carefully investigated. 
Comparison of the various sections will show how those at Row differ from the others. 

Observations between Barreman and Clynder. — A few observations were taken at 
this point, about midway between Row II. and Shandon, in the form of a cross section, 
which is of value as showing the relation of axial to lateral vertical temperature curves, 
and giving some information as to the form of the isothermal sheets. The observations 
were practically simultaneous, that off Barreman pier in 2 fathoms being made at 13 h 15, 
the three deep-water soundings at 13 h 30, 14''0, and 14''20, and the others immediately 
after. They were made on June 7th during a strong easterly breeze, the "Medusa" 
going against the wind from the lee to the weather shore. 

The vertical curves were defined by very numerous observations, so that a cross 
section could be drawn with some confidence. 

The data are as follows. Air temperature, 52 0- l : — 

Table XL. — Cross Section of Gareloch at Chjndcr. 



No. and depth .... 


1 (2 fms.) 


2(13fms.) 


3(16fms.) 


4(1 2 fms.) 


5(3?) 


6 (6 fms.) 


7 (4 fms.) 


No. of points .... 


o 


9 


9 


9 


3 


6 


3 


Temperature, surface 


48-3 


48-0 


47-3 


L-7-5 


47-4 


47-0 


47-0 


Temperature, bottom 


is-:; 


46T 


45-9 


46T 


47-1 


46-6 


46-9 


Temperature, mean 


is-:! 


467 


46-4 


46-6 


47-3 


46-8 


46-9 



The diminution of mean temperature is here uniform with the increase of depth. At this 
point the width of the loch is exactly 1 mile. 

From the curves a Election (fig. 45, Plate XXXI.) was drawn on a large scale, the iso- 
therms of each quarter of a, degree being represented upon it. On account of the great 
closeness of the thermometer readings, this could be done with considerable exactness. 
The result showed a remarkable decrease of temperature to windward, most rapid near 



CLYDE SEA AEEA. 107 

both shores, and least in the centre. The isotherms dipped from the west shore up to 
the surface, showing a greatly thickened layer of warm water against that shore. The 
temperature of 47° left the west side at 5 fathoms, crossed the centre at 4 fathoms, and 
curved up sharply to the surface at Station 6. While the isotherm of 46°'75 ran 
parallel half a fathom deeper from the west shore to Station 4, whence it rose to 3^ 
fathoms at Station 6, and thence dipped to 4 fathoms at the eastern shore ; the line of 
46°'5 ran on the whole parallel and about half a fathom deeper, and below it the fall of 
temperature was gradual, the isotherms being highest in the centre and lowest at both 
sides. Two bands of close-clustered isotherms cross the section, showing two planes of 
juxtaposition of layers of unequal temperature ; between these are the thoroughly mixed 
areas, which occur on the west shore, in the centre, and on the east shore. On the west 
side of the central line the temperature rises toward the west shore at every level, 
showing a descent and banking up of the warmer upper layer. On the east side, from 
4 fathoms to the surface the temperature was practically uniform, and cooler than the 
rest of the surface, showing an upward movement, but more feeble than that in the 
centre ; and below 4 fathoms the isotherms dip down from the' centre eastward as well 
as westward, showing the descent of warmer water along the windward side. 

The natural conclusion to draw from this is that at about 5 fathoms the windward 
side is divided into an upper zone of direct wind circulation, and a lower zone or eddy 
of inverted wind circulation, as shown roughly on the diagram fig. 39, Plate XXIX., 
while the leeward side has a complete system of direct circulation, the power of the 
wind causing an upward current in the centre as well as against the shore. 

Observations at Shandon. — Soundings were made in mid-channel off Shanclon Pier, 
in line with Ma-more Farm on the opposite side, in a depth of 21 fathoms. About 
a quarter of a mile higher up, the greatest depth (23 fathoms) occurs. Sections are given 
in Plate 9, fig. 17b, in Part I. 

The density of the water was as follows : — 

Surface (10 observations). Bottom (9 observations). 

Mean, 1-02233 102353 

Maximum, 1-02378 1-02398 

Minimum, 101914 102323 

The bottom water of the G-areloch is the least dense of any in the Clyde Sea Area, 
excluding the estuary. 

The great range between the temperature of surface and bottom layers is noticeable, 
particularly in the cases of maximum positive slope in early summer ; but the form of 
the curves is of interest as well. Nos. 1, 5, 18 may be excluded from consideration on 
account of the small number of observations made, and in the case of No. 5 on account of 
the very exceptional form. No. 1 8 showed the maximum positive slope, 3° "6 in 20 fathoms, 
but No. 12, with 3°"2, is more trustworthy. The maximum negative slope was 2°"4, 
shown in No. 7. Both maximum positive slopes occurred in August (1887 and 1888) 



108 



DR HUGH ROBERT MILL ON THE 



and two maximum negative slopes in November, the third in December. But in August 
1886 the positive slope was only 0° - 6, and the curve below 2 fathoms (No. 4) was 
practically homothermic. This was probably an accidental result, due to temporary 
mixture by winds. 

There were two well-marked types of curve at this station, one paraboloid or 
approaching the hyperbola, the other S-shaped, and at opposite seasons both curves 



Table XLI. — Temperature Observations at Shandon. 



No. . . . 

Date . . . 
No. of Points 
Temp. . . . 
Slope . . . 



1 

13.4.86 

3 

41-4 
+ 1-9 



2 

21.4.86 

7 

42-0 
+ 1-2 



3 

16.6.86 
6 

47-6 
+ 1-8 



4 
3.8.86 

7 

52-9 
+ 0-6 



5 

24.9.86 

4 

54-4 
+ 0-7 



11.11.86 
6 

50-5 
-1-7 



28.12.86 
6 

44-4 
-2-4 



8 


9 


10 


2.2.87 


25.3.87 


6.5.87 


6 


6 


6 


43-1 


42-9 


45-7 


-1-0 


-o-i 


+ 1-6 



11 

13.6.87 
9 
50-4 

+ 2-8 



No. . . . 

Date 

No. of Points 

Temp. . . . 

Slope . . . 



12 

6.8.87 

9 

57-4 
+ 3-2 



13 

30.9.87 

4 

54-1 
-0-2 



14 

29.11.87 
6 

46-8 
-1-7 



15 

9.2.88 
6 

43-8 
-0-3 



16 
28.3.88 
3 
42-0 



17 
7.6.88 
6 
46-5 



-0-1 i +1-3 



18 

20.8.88 

3 

52-8 
+ 3-6 



19 

6.9.88 

6 

53-6 
+ 2-0 



20 
22.10.88 

6 

49-9 
-0-3 



21 

25.10.88 

6 

50-0 
-0-1 



showed reversed slopes. These forms were only hinted at in the Eow II. observations. 
Representative examples are given in fig. 46, Plate XXXI. Nos. 7 and 10 were the two 
best marked hyperbolas. No. 7 (December 1886) was a cooling curve of high negative 
slope ; it indicated the existence of 5 fathoms of surface water (from 41° surface to 44°'l), 
showing a rapid rise of temperature with depth, separated by an intermediate layer 
from 10 fathoms of almost uniform temperature (44° - 9 to 45° - l). No. 10 is a 
warming curve (May 1887), showing high positive slope. The change here is 
remarkably abrupt. From the bottom at 20 fathoms to 5 fathoms the temperature 
rises only from 45°"2 to 45°*3, showing that three-quarters of the mass is homothermic. 
From the depth of 3 fathoms, with temperature 45° - 6, the water heats rapidly to 49°'3 
on the surface. In this case three observations — surface, 5 fathoms, and bottom — would 
have sufficed to determine the true character of the temperature distribution, but if the 
three observations had been at any intermediate position, they would have been mis- 
leading. 

The S-shaped curve was shown fairly well in the central stations of the Clynder 
observations. It indicates a stratified or heterothermic arrangement of layers of water 
at different temperatures. The best examples shown at Shandon were Nos. 6 (negative) 
find 3, 11, and 12 (positive). Here many and close observations are required to define 
the various inflections, and No. 11 is the best. The typical S-curve shows the following 



CLYDE SEA AREA. 109 

peculiarities. The curve of mean temperature is a straight line passing through the 
surface, centre, and bottom of the S. In the positive curve the upper 10 fathoms 
show temperatures below the mean curve, the lower 10 fathoms show temperatures 
correspondingly above the mean. The positive curves of this type occurred in June and 
August, the negative in November. They show typically in summer rapidly warming 
surface and bottom water, and a large mass of nearly uniform temperature between, 
colder than the surface and warmer than the bottom layer. 

The mean temperature of 20 soundings (12 in the summer, 8 in the winter half- 
year) was 48°, maximum 57°'4 in August 1887, minimum 41 0, 4 in April 1886. 

Partial Cross-Section on June 7th, 1888. — At 12 h 15 a sounding was made at the 
deepest point in mid-channel, and at 12 h 40 another off Shandon Pier in 6 fathoms. 
The former showed much higher temperatures at the same depth, the isotherms sinking 
abruptly to windward. At 15"40 a sounding was made in 4 fathoms off the pier, and 
at 16 h 10 another on the western and leeward shore directly opposite. This showed a 
well-marked rise of temperature on the leeward as compared with the windward shore. 
In the three hours, however, the temperature off Shandon had risen 1°, and the dip of 
the isotherms was altered. Hence the section which was drawn cannot be compared 
with that off Clynder, although it appears to show similar features in a less marked way. 

On October 22nd, 1888, at ll h 20, wind R, very light, and on October 25th at 
ll h 10, wind S.W. by S., a stiff breeze, observations were made with great com- 
pleteness. The mean temperatures as deduced from these curves was practically 
the same, 49°"9 for the former, 50 o, for the latter, so that, on the whole, they 
represent a complete cessation of cooling during three days in Autumn. The average 
temperature of the lowest 5 fathoms was unchanged, that of the superficial 5 fathoms 
was uniformly raised by o, 2, a result probably due to the surface action of the strong 
wind blowing up the loch on the second occasion. The intermediate layer was slightly 
cooler on the second occasion, evidently showing that in the three days there had been first 
cooling down to at least 10 fathoms, where it must have amounted to more than 0°"1, 
and subsequently a uniform warming of the surface layers. 

The relation of change of temperature to depth and time at Shandon is shown in the 
diagram fig. 9, PI. V., in which the tendency towards homothermic change of tempera- 
ture is made evident. Only at the maximum of 1887 and 1888, and at the minimum of 
1888, are there clear traces of change of temperature taking place much more rapidly on 
the surface than at the bottom. 

Observations at Garelochhead. — Soundings were made in mid-channel, ^ of a mile from 
the head of the loch in a depth of 10 fathoms, shoaling rapidly to the head. (See section 
17a, PI. 9, in Part I.) The average density of the water at this station was as follows : — 

Surface, 11 observations. Bottom, 9 observations. 

Mean, 102238 .... 1-02339 

Maximum, 1-02390 .... 1-02396 

Minimum, 101913 .... 102287 



11(1 



DR HUGH ROBERT MILL ON THE 



The average density at the head was greater than that at Shandon, but the extremes 



Mere also greater. 



Table XLII. — Temperatwre Observations at Garelochhead. 



No 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


Date 


13.4.86 


21.4.86 


16.6.86 


3.8.86 


24.9.86 


11.11.86 


28.12.86 


2.2.87 


25.3.87 


6.5.87 


No. of Points 


4 


7 


4 


4 


4 


3 


6 


3 


3 


5 


Temperature 


41 -6 


4-1-0 


47-9 


53 T 


53-9 


50-1 


43-8 


42-9 


43-0 


46-4 


Slope 


+ 1-1 


+ 1-8 


+ 0-6 


+ 04 


-0-2 


-0-7 


-1-8 


-0-7 


-0-1 


+ L8 


No 


11 


12 


13 


14 


15 


16 


17 


18 


19 




Late 


13.6.87 


6.8.87 


30.9.87 


29.11.87 


9.2.88 


28.3.88 


7.6.88 


20.8.88 


6.9.88 




No. of Points 


3 


6 


4 


3 


3 


3 


3 


3 


3 




Temperature 


51-0 


58-5 


54-4 


44-9 


43-6 


41-7 


47-7 


55-7 


54-8 




Slope 


+ 0-7 


+ 1-2 


-01 


-1-7 


o-o 


o-o 


+ 0-9 


+ 2-4 


+ 0-5 





The mean of these curves gives 48°"3 as the average temperature of the station, which 
is a little higher than any other average temperature in the loch; the range from 41° *6 
in April 188G (41°7 in March 1888) to 58°'5 in August 1887 is also the largest found. 
On account of the slight depth comparatively little interest attaches to the form of the 
individual curves, which were only delineated satisfactorily in a few cases. So far as the 
depth admitted, the forms of paraboloid and S-shaped curves, and the changes of slope, 
were shown as at Shandon. No. 12 is an interesting case of a paraboloid curve formed 
perfectly from 2 fathoms downwards, but turned up abruptly to the surface where the 
temperature was 3° lower than the rest of the curve would lead one to expect. The 
correctness of surface temperatures, as a rule, is open to doubt. In curve 10, for instance, 
a surface reading, when the observations began, gave 52°. and when they were over, only 
50°5. A further fall of 0°'9 would have given the same form of curve as in No. 12. 

No. 10 was made at lG h 40 on May 6th, 1887, No. 12 on August 6th, 1887, at 13 h 45 in 
rain. 

The three maxima embraced by the observation show Garelochhead to have the 

highest temperature, and Row I. the lowest, Row II. and Shandon lying close together. 

At the three minima the Garelochhead curve is almost the same as the others, but it 

Bhowa a tendency to rise and fall more rapidly, thus having a slightly longer warm 

and cold season, and slightly shorter transition seasons than the other stations. 

It is interesting to observe that the difference in mean temperature of the vertical section 

between the different stations is greatest at the Autumnal maximum, and least (practically 

imperceptible) at the Spring minimum. 



& 



CLYDE SEA AREA. Ill 

The range of temperature between surface and bottom layers, as would be expected 
from the depth, is considerably less than for Shandon ; but the dates of change from 
positive to negative slope are practically the same, coinciding with the seasonal maximum 
and minimum, the former in September, the latter in March. 

Temperature Sections of Gareloch. — Temperature sections were drawn for each trip, 
and are reproduced in Plate. XVI., figs. I. to XVII. 

Section I., April 13th, 1886. — The weather was practically dead calm, anticyclonic, 
with air-temperature below the average of the month. Observations were made at all 
stations, the average temperature of the loch being 41 0, 8, and of the superficial 5 fathoms 
42 0, 7. The isotherm of 42° was at 6 fathoms at Row I., 4 fathoms at Row II., and at 
2^- fathoms at Garelochhead. The other isotherms ran fairly parallel, and especially in 
the seaward half of the loch showed a marked dip toward the mouth, such as suggests an 
upwelling of colder deep layers about Shandon, or a less rapid heating of the water just 
inside the bar. The upper half of the loch showed practically horizontal isotherms indi- 
cating a tranquil condition. The observations were all made nearly at low tide. 

Section II, April 21st, 1886. — Observations being made only at Shandon and Gare- 
lochhead, this section is confined to the upper half of the loch. The weather up to the 
18th had been calm, on the 19th there was a north-easterly breeze, on the 20th an E.N.E. 
gale, and on the 21st there was a breeze from north-east blowing obliquely down the 
loch. Great temperature disturbances had taken place. The mean vertical temperature 
at Shandon had risen from 41°"4 to 42°'0, that at Garelochhead from 41°"6 to 43°'0. The 
great mass of the water was close to 42°, but varied irregularly. At Shandon the 
isotherms from 44° - 5 to 42° were crowded into the superficial 1|- fathoms ; at the head 
those from 45° to 42° were spread through the upper 5 fathoms. There thus appeared 
to be a distinct heading up of warm surface water, the isotherms all dipping to the head 
of the loch, where the surface water had been considerably freshened. The state of 
matters was such as could be readily explained by the action of a southerly wind, but the 
wind had blown only from the north-east since the calm. It is, of course, possible that 
the easterly component drove estuary water into the Gareloch, but this does not seem 
to be the case ; and the section stands an interesting exception to the usual action of the 
wind. The result is very probably due to deep tidal effects ; observations were made 
nearly at high-water. The intermediate minimum of temperature is too slight to be 
profitably discussed. 

Section III, June 16th, 1886. — Here warming had gone on rapidly, the mean tempera- 
ture of the loch being 48°"1, and of the superficial 5 fathoms 48°"5. The water was well 
stratified, the isotherms dipping strongly toward the mouth, and the bar seemed to have 
no effect on them. The isotherm of 48° was at a depth of 15 fathoms at Row II., 
9 fathoms at Shandon, and only 2^ fathoms at Garelochhead. The higher isotherms were 
farther apart than the lower, showing a more thorough equalisation of temperature, 
contrary to what would be expected during warming-up. An anticyclone had prevailed 
from June 1st to 9th, followed by a cyclone, which on the 16th caused a stiff breeze from 



112 DR HUGH ROBERT MILL ON THE 

a point or two north of west. This showed the full action of the northerly component, 
and taken in conjunction with the conditions of Section II., suggested that in the 
( rareloch an east wind acts as if it blew up, a west wind as if it blew down. 

The tide throughout was in the first quarter of ebb, and thus, as in the previous case, 
the disturbance of the strata was probably in large measure tidal. 

Section IV., August 3rd, 4th, 1886. — The average temperature of the loch was 52°-9, 
and of the superficial 5 fathoms 53 0, 1. The two landward stations were observed on 
August 3rd, with the tide about half ebb, and showed nearly uniform temperature, with 
nearly horizontal isotherms having a slight seaward dip. The two seaward stations 
observed on the 4th, just after low-water, showed strong landward dip of the isotherms, 
and the bar showed a very marked effect of separating the colder water outside from the 
warmer within. Thus at Row I. the temperature was 52°'l at the surface, and 51°*3 
at the bottom ; at Row II. it was 53° - 3 at the surface, 52° *2 at the bottom. Between 
Row II. and Shandon the isotherms dipped gently landward, 

The wind was variable, on account of the rapid passage of small cyclones ; on the 3rd 
there was a light westerly wind, and on the 4th a light south-easterly, which would 
partly account for the steep dip of isotherms at the mouth. 

Section V., September 24th, 1886. — The tide was in the first quarter of ebb, and the 
section shows at Shandon an exceptionally well-marked intermediate maximum, the 
traces of which are distinctly seen at G-aretachhead. It is unfortunate that the observation 
at Row II. was omitted on this trip, but there are indications that the intermediate 
maximum did not extend so far. From September 10th to 22nd an anticyclone had 
kept up light variable breezes ; the 24th, when the observation was made, was dead calm. 
The salinity conditions were somewhat peculiar, the water at the head on the surface 
being Salter than at either of the other stations ; that at Shandon was freshest. The 
average temperature of the loch was 53° '9. 

Here the surface water, cooling rapidly, seems to have floated on the warmer layers 
below, which preserved the natural summer distribution of cooling downward to the 
bottom. 

A similar though less marked distribution of temperature occurred a year later. See 
Section XIII. 

Section VI, November 11th, 1886. — The average temperature was 50°, that of the 
upper 5 fathoms 49° '5. The distribution was comparatively simple, cooling being in pro- 
gress from the surface downward. But there was a distinct trace of an intermediate 
maximum at Shandon, lying very much nearer the bottom than in Section V. There 
was a general gentle dip of the isotherms seaward from Garelochhead to Row II., but 
a sharp dip landward from Row I. to Row II., the result being that at Row II. the cold 
layer was thicker than anywhere else. This may partly be accounted for by the fact that 
the Row stations were observed about half-an-hour before and the others about half-an- 
hour after high-water. The tidal streams about high-water are, however, relatively 
feeble. 



CLYDE SEA AREA. 113 

Garelochliead had the saltest, Row I. the freshest surface water in the basin, a result 
probably due to the flood-tide carrying in brackish estuary water. The weather was 
dead calm. There had been strong south-westerly winds from the 1st to the 4th, 
and after that date very disturbed weather. 

Section VII., December 28th, 1886. — Mean temperature of loch 44° *2, of superficial 
five fathoms 43° *2. The cold surface layer was thinnest, but with greatest range of 
temperature at Garelochliead. The isotherms of the surface 3 fathoms dipped gently 
landward, below that level gently seaward. The tide was close to high -water. The 
wind was blowing a gale from the north-west and west, in a general way down the 
loch, but the tide appears to have more than neutralised its effect in disturbing the 
layers of water except, curiously enough, at the mouth. 

The warmest water inside the bar was 45°'l on the bottom, that outside was 46°"0 on 
the bottom, where the depth was only half as great as inside. 

Section VIII. , February 12th, 1887. — The mean temperature of the mass was 42°"8. 
The isotherm of 42°"5 ran horizontally at 2 fathoms ; the others (43° and 43°*5 
alone appeared) dipping very gently seaward. The tide was in the second quarter of 
flood, and the weather was anticyclonic on the 1 2th, with a light south-easterly breeze. 
A remarkably uniform distribution of temperature prevailed, showing the winter 
cooling of the basin practically completed. 

Section IX., March 2btli, 1887. — The temperature of the mass of water was 43 o, 0, 
almost the same as for Section VIII., but the upper 5 fathoms had become somewhat 
wanner. The range of temperature being less than half a degree, it is impossible to 
draw any conclusions regarding circulation from this section. A north-westerly gale 
was blowing while the observations were taken, and the tide was in the first quarter of 
ebb, hence there was a strong current setting out. 

Section X., May 6th, 1887. — The mean temperature of the section was 46°'0, and 
that of the upper 5 fathoms, 46° '7, showing progressive heating, especially in the upper 
layers, and toward the head of the loch. The line of 46° ran from the sill of 
the bar (5 fathoms) to 2\ fathoms at the head. It so happened that a partial observation 
was made off Clynder, which showed that the isotherms of the upper 2 fathoms clipped 
thence landward to the head, while those from 2 to 5 fathoms dipped seaward ; but from 
Clynder to Row II. the dip was landward throughout, thus showing a considerable 
upwelling on the bar. The tidal phase was low- water at Shandon, and the beginning of 
flood at Row. The wind was south-east, and light. The surface water warmed up very 
rapidly from Row to the head. The appearance was that of an upwelling of colder water 
at Row, combined with strong sun-heating, and perhaps slight accumulation of surface 
water at the Garelochliead. 

Section XL, June 13th, 1887. — Rapid warming had gone on from the surface, the 
mass-temperature being now 50°'7, and the upper 5 fathoms 51°-4. Stratification was 
distinct, the isotherms below 5 fathoms dipping gently seaward, and above that level 
showing an accumulation of warmer surface water about Shandon, and of cooler water 

VOL. XXXVIII. PART I. (NO. 1). P 



114 DR HUGH ROBERT MILL ON THE 

about Row, indicating cold up welling at the latter place. The most rapid change of 
temperature with depth occurred (at Shandon) from 15 to 20 fathoms, where there 
was a marked crowding of the isotherms. The tide was at the last quarter of ebb, and 
a very light south-westerly breeze was blowing, the conditions being anticyclonic. 

Section XII., August 6th, 1887. — This section represents the loch at the maximum 
temperature ever found, and nearly at the greatest range of vertical temperature. The 
mean was 57°' ( J, and of the upper 5 fathoms 58°'5. The isotherms dipped steadily land- 
ward, and showed a nearly vertical arrangement at the bar, which separates water of 
markedly different temperature. The loch was stratified into a thin top layer of water 
very warm on the surface, a thick well-mixed intermediate stratum, and a thinner bottom 
layer at Shandon of rapidly diminishing temperature. It is noteworthy that the water 
from 57° to 5 4° "4 at Shandon was quite cut off by bottom water over 57°*4 from the cooler 
water outside the bar. Altogether this section is a characteristic example of great surface 
heating. The weather was calm, and the tide at half flood, the latter probably accounting 
for the landward dip of the isotherms. 

Section XIII. , September 30th, 1887. — Average temperature, 54° '0, and of upper- 
layer of 5 fathoms 53°*9. An excellent example of surface cooling, leaving the great 
mass of water over 54°, with a thin surface zone and a thinner bottom zone (at the ends 
of the loch only) slightly cooler. The range of temperature is too slight to discuss move- 
ments, the whole mass of water being fairly well mixed. 

Section XIV., November 29th, 1887. — The mass-temperature had now become 46°*1 
(the surface layer of five fathoms being 45° "6). The section showed rapid cooling in 
progress. The upper layer, colder than 46°, was compressed within two fathoms at 
Shandon, and 1 fathom at Row I., but expanded to 5 fathoms at Row IT., and 8 
fathoms at the head. This seems to indicate upwelling at Shandon, and down-sinking 
at Row and Garelochhead, the Row bar keeping out the warmer deep water. 

There was a very light north-easterly breeze, and the tide was in the last half of flood. 

Section XV., February 9th, 1888. — The mean temperature of the section was 43°'7, 
and that of the surface layer 43° "5, very similar to the conditions shown in Section VII. 
The temperature was practically uniform, and the two isotherms which appear run 
parallel to the configuration of the basin, i.e., they indicate a slight upw T elling at both 
ends. The wind was N.W., nearly down loch, and the tide in the last quarter of 
flood, or setting up loch ; the former would perhaps account for the slight upwelling 
at the head, the latter for that at the mouth. 

Section XVI., March 28th, 1888. — The mean temperature was 4 1 0, 9, practically the 
same as in Section I. The tidal phase was low-water, and a strong north-east wind blew. 
Homothermic conditions prevailed throughout, showing thorough mixture. The total 
range of temperature was in fact only 0°*3, the surface being coolest. 

Section XVII, June 7th, 1888. — Gradual warming from above here appears. The 
mass-temperature had reached 4G°7, and the isotherms steadily dipped landward. An 
unusual lapse of time separated the observations at Garelochhead and at Row, the tide 



CLYDE SEA AHEA. 115 

beino- -?- hours ebb at the former, and 4l hours ebb at the latter. A strong east 
wind was blowing, leading to well marked banking up of warm surface-water against the 
eastern side (see p. 106). The cross-section shows that the rise of surface isotherms in the 
longitudinal section at Clynder is due to the colder water drawn up on the windward side 
and driven across the loch. The same thing probably happened, though perhaps in a 
less degree, elsewhere. The mass of relatively cold water which stretched along the 
bottom from the lip of the barrier diagonally to beyond Shandon is exaggerated in 
the section by the dividing isotherm happening to be one at which the colour is changed, 
the temperature below 46° (or even 40° \5) being practically uniform to the bottom. 

Section XVIII., August 20th, 1888. — There were only two sets of soundings, but 
these showed for the head of the loch the greatest range of vertical temperature ever 
observed in summer. Below 54° at 5 fathoms the isotherms were practically parallel 
and horizontal. Above that level they dipped landward, the water on the surface rapidly 
growing warmer to Garelochhead. The weather was calm, and the tide rather more than 
half ebb. 

Section XIX., September Gth, 1888. — The average mass-temperature was 54°"1, and 
that of the upper 5 fathoms 54°*7. The isotherms showed a very slight dip landward at 
the head, and a very slight dip seaward at the mouth, except between Row I. and II. The 
section seems to show the commencement of seasonal cooling. A strong, squally S.W. to 
W.S.W. wind was blowing, and the tide was about quarter ebb. 

The three Sections for June are representative of the conditions of rapid heating. 

In June J 886 there was the most perfect instance of parallel isotherms dipping 
seaward, each of the three isotherms of which more than two points were fixed being 
almost straight lines. The strata of water seemed in fact to be uniformly displaced or 
tilted so as to bring up the cold lower layers against the head-slope, and to bring down 
the warm upper layers on the barrier. 

In June 1887, with higher temperature and greater range, the isotherms were also 
remarkably straight and parallel, dipping seaward, but more gently than in 1886. The 
upper isotherms were somewhat irregular. 

In June 1888 the isotherms present on the whole the best example of landward dip, 
the only other instance at all well marked of an accumulation of surface water at the 
head being in Sections XII. and XIV., August and November 1887 — both cases of 
flood-tide. 

All the June observations were made during the first half of ebb ; and the great range 
of temperature makes them particularly useful for the purpose of detecting evidence 
of the circulation of water by means of the direction of isotherms. 

The phenomena associated with the Bar off Row Point are well brought out in 
several of the sections. Out of the whole number of 19, there are 13 sections in which 
observations were made at Row I. and at Row II., on both sides of the shallow bar 
which separates the Gareloch from the Estuary. In six of the cases the isotherms (with 



110 DR HUGH ROBERT MILL ON THE 

one exception at flood-tide) dip landward from Row I. to II.; in six of the cases (with 
practically only one exception at ebb-tide) they dipped seaward from Row II. to I. ; and 
one case was indeterminate. The indeterminate case was Section XVI., the observations 
being made at low- water, when the whole mass of water was within o, 2 of 42°. 

The six instances of landward-dipping isotherms were observed in February 1888, 
August 188(5, August 1887, September 1888, November 1886, and November 1887. 
They are thus all cases in which the water, as a whole, was at a maximum or cooling. 
The February instance is peculiar in showing a minimum temperature in the middle 
depths inside the loch, and in having too few isotherms to justify discussion. It 
may accordingly be passed over. The September Section, No. XIX., is also excep- 
tional, as it shows a maximum temperature in the middle layers outside the bar, and 
it is also the only one in which this form of dip occurs with an ebb-tide. It shows 
the uprising and outflowing of water between 54° and 55° over the bar, but at the time 
the wind was blowing strongly against the tide, and there are signs of this action driving 
in rather cooler surface water, and compelling the ebb-tide to escape as an undercurrent. 
Distinct traces of banking up by wind at the head of the loch are shown. The remaining 
four cases may be taken as typical. In both the August cases the tide at Row was in 
the first quarter of flood, in one case (No. IV.) with a wind blowing into the loch, in 
the other (No. XII.) it was calm. In both, colder water is entering, and in both the 
bar seems to stop the deeper and colder layers outside from getting in. In fact the 
surface temperature at Row I. is found (judging by the isotherms) on the sill of the 
bar; the horizontal stratum in line with the bar being 0°"5 in one case and 1°"5 in 
the other colder at Row I. than on the bar. The two November sections show a 
substantially similar state of matters, except that the water entering was then warmer 
than that inside, but it entered in the same way, affecting most the surface about 
Row II. 

If we may look on the isotherms as representing originally-horizontal planes between 
layers of water of different temperature, and suppose that these layers do not change in 
temperature, the inflection of the isotherms indicates that the water from outside pushes 
against and bends up those layers, driving the bent-up portions back into the loch on 
the surface, and so thickening them at the lines of inflection. In other words, it proves 
that the tide is mainly a mass movement, bringing up the outer water — warmer or colder 
according to the season — against the inner waters, pushing the latter forward bodily, not 
slipping under and lifting them up, as is the case in a tidal river. The bar effectually 
prevents mixture below its level, and also prevents the mere slipping to and fro of a 
mass of water cut off horizontally above. It acts like the continental edge on oceanic 
isotherms, causing a disturbance in the distribution of the water to a considerable 
depth, and forcing up the deep layers to the surface, so that in these conditions of 
flood-tide Row I. has the deep temperature raised much nearer the surface than Row II., 
showing strong up welling. 

It is unfortunate that observations were not made on the shallowest point of 



CLYDE SEA AREA. 117 

the bar, where, in all probability, the isotherms would be found still nearer the surface 
than at Row L, and the slope to Row II. would be proportionally intensified. 

The six cases of seaward-sloping isotherms occurred in March 1887, April 1886, May 
1887, June 1886, June 1887, and December 1886. Thus all with one exception occurred 
during the process of warming up, and all with the same exception at ebb-tide or at low- 
water. This exceptional case was the only one in which an intermediate minimum 
temperature was observed. It occurred during a down-loch gale, which might have 
accelerated ebb-tide, as the Row observations were made just before high-water. The 
Section for March must also be passed by, as the whole water, inside and outside, was 
practically at uniform temperature. No. I., April 1886, was observed at \ hour flood, 
and while the lower isotherms dipped seaward, the upper dipped landward. The 
weather was calm. Here we observe the upper layer of warmer water steadily thicken- 
ing toward and beyond the mouth of the loch as the flood-tide was beginning to enter. 
The May section, at low-water, shows the isotherms practically horizontal across 
the bar. The section for June 1886 also shows the bar as producing no apparent 
effect on a down-loch wind distribution ; and the section for June 1887 shows 
only a slight dip. 

It is unfortunate that practically all the warming-up sections should have been 
observed with an ebb-tide, and all the cooling-down sections with a flood- tide ; but a 
consideration of the diagrams makes it seem likely that it is a tidal rather than a 
seasonal effect which brings out the typical forms of isothermal dip in the case of the 
Gareloch. On the other hand, it may be that all we can safely say is : During the 
months of maximum temperature and of rapid cooling the contrast of temperature 
between the water inside and outside the Gareloch is much greater than it is during the 
months of minimum temperature and of rapid warming. 

Mean Temperature of Gareloch. — The mean temperature of the mass of water 
in the Gareloch was calculated in two different ways. As the depression is of 
comparatively uniform depth, and the several stations rarely differ much in mean 
temperature, it seemed reasonable to take the average of the vertical temperature 
means as that of the whole section. This is done in Table XLIIL, cases where 
one or more observations were omitted being supplied by a probable value. The 
last column of this table gives the mean temperature calculated from the 
temperature sections by measuring the areas between adjacent isotherms and making 
allowance for the volumes of the 10-fathom slices of water. The temperature of 
the upper slice of 10 fathoms being a, and that of the lower b, the mean temperature 

was calculated by the formula T= - , _, . Details of this measurement are given in 

4 7 & 

Table XLIV. It is remarkable how closely the two estimates correspond, the mean of 
the nineteen temperature trips being identical when estimated in either way. The 
greatest deviations were o, 5 in August 1886, 0°-6 in August 1887, and o, 4 in November 
1887. 



118 



DR HUGH ROBERT MILL ON THE 



Table XLIII. — Mean Temperature of Vertical Soundings, Gareloch. 



Trip. 


Date. 


Row I. 


Row II. 


Shandon. 


Head. 


Mean. 


Mean from 
Section. 


I. 


13th April 1886, 


42-3 


41-8 


41-4 


41-6 


41-8 


41-77 


II. 


21st „ „ 


42 - 8 


42'3 


42-0 


43-0 


42-5 




III. 


16th June „ 


48-7 


48-3 


47-6 


47-9 


48-1 


48-07 


IV. 


/ 3rd August „ ( 
1 4th „ „ J 


51-6 


52-6 


52-9 


53-1 


1 52-5 


52-96 


V. 


24th September „ 


53-1 


54'° 


54-4 


53-9 


53-8 


53-96 


VI. 


11th November ,, 


50-2 


49-4 


50-5 


50-1 


50-0 


50-03 


VII. 


28th December „ 


44-0 


44-4 


44-4 


43-8 


44-1 


44-24 


VIII. 


12 th February 1887, 


43" 1 


42-9 


43-1 


42-9 


43-0 


42-85 


IX. 


25th March 


43-0 


42-9 


42-9 


43 


43-0 


43-00 


X. 


6 th May „ 


46-1 


45-9 


45-7 


46-4 


46-0 


46-00 


XL 


13th June ,, 


51-0 


50-6 


50-4 


51-0 


50-7 


50-75 


XII. 


6th August ,, 


55-8 


57-6 


57-4 


58-5 


57 3 


57-92 


XIII. 


30th September „ 


54"° 


53-9 


54-1 


54-4 


54-1 


54-02 


XIV. 


29th November „ 


47-7 


46-6 


46-8 


449 


46-5 


46-09 


XV. 


9th February 1888, 


44-5 


44-0 


43 '8 


43-6 


44-0 


43-70 


XVI. 


28th March 


41-8 


419 


42 


41-7 


4L9 


41-91 


XVII. 


7th June „ 


46-5 


46-3 


46-5 


47-7 


46-7 


46-72 


XVIII. 


20th August 


52-6 


53'° 


52-8 


55-7 


53-5 




XIX. 


6th September „ 
Mean, 


53-7 


54-1 


53-6 


54-9 


54-1 


54-15 


48-0 


48-0 


48-0 


48-3 


48-1 


48-11 



Table XLIV. — Mean Temperature at Various Depths in the Gareloch. 



Trip. 
I. 


Date. 


Days 

since 

last 

Trip. 


Mean 

Temp. 

Weighted 


Diff. 
from 
last 
Trip. 


Change 
per day. 


Temp. 
0-10 fms. 


Change 

per day, 

0-10 fms. 


Temp. 

10-20 

fms. 


Change 

per day, 

10-20 fms. 


13.4.86 




41-77 






42*00 




40-95 




III. 


16.6.86 


64 


48-07 


+ 6-30 


+ 0*098 


48-23 


+ 0-097 


47-46 


+ - I02 


IV. 


3.8.86 


48 


5296 


+ 4-89 


+ 0'I02 


53-05 


+ o - ioo 


52*64 


+ OT08 


V. 


24.9.86 


52 


53'96 


+ 1-00 


+ 0'020 


54-06 


+ 0'020 


53*58 


+ 0-018 


VI. 


11.11.86 


48 


50-03 


+ 3-93 


— 0-082 


49-78 


- 0-089 


50-96 


-o"°55 


VII. 


28.12.86 


47 


44-24 


-5'79 


-0-123 


44-04 


- 0*122 


44-96 


— 0*128 


VIII. 


12.2.87 


46 


42-85 


-1-39 


— 0*030 


42-71 


- 0*029 


43-35 


-° >0 35 


IX. 


25.3.87 


41 


43-00 


+ 0-15 


+ 0-004 


43-00 


+ 0*007 


43*00 


- 0*001 


X. 


6.5.87 


42 


46-00 


+ 3-00 


+ 0*071 


46*20 


+ 0*076 


45*25 


+ 0-054 


XI. 


13.6.87 


30 


50-75 


+ 3-75 


+ 0*125 


51*00 


+ 0*160 


49-82 


+ 0-152 


XII. 


6.8.87 


62 


57-92 


+ 7-17 


+ 0116 


58-16 


+ 0-II5 


57-02 


+ o - n6 


XIII. 


30.9.87 


55 


54-02 


- 3-90 


- 0-071 


54*02 


-O-075 


54-00 


-o'°55 


XIV. 


29.11.S7 


60 


46-09 


-7-93 


-0-132 


45*81 


-0*137 


47-14 


- 0*114 


XV. 


9.2.88 


72 


43-70 


- 2-39 


- o'o33 


43*65 


- 0*030 


43*87 


- 0*045 


XVI. 


28.3.88 


47 


41-91 


-1-79 


- 0-038 


41-89 


-0*037 


42-00 


- 0*040 


XVII. 


7.6.88 


72 


46-72 


+ 4-81 


-f 0-067 


46*90 


+ 0*070 


46-07 


+ 0-057 


XIX. 


6.9.88 


91 


54-15 


+ 7-43 


+ C082 


54*37 


+ 0-083 


53*33 


+ o - o8o 



CLYDE SEA AREA. 119 

As these tables show, the loch was in an almost perfectly homothermic state at the 
period of annual minimum in March or April, and returned to a similar condition in 
September or October, just after the annual maximum. At other times there was a con- 
siderable range of temperature between surface and bottom, and also between the mean 
vertical temperatures at the various stations, the range from one to another being 1° or 
2°. The change of temperature between contiguous stations seems to be due as much to 
the influence of wind as to that of season. 

In order to allow an exact comparison to be made with the other natural divisions, the 
temperature of the surface layer 5 fathoms deep was calculated, and the result is expressed 
together with the mean in the curves of fig. 47, Plate XXXI. , on which the average 
monthly temperature of the air at Helensburgh is also shown. For the whole period 
under observation the average temperature of the superficial slice of water was identical 
with that of the mass, being a fraction of a degree higher during the season of heating, 
and a fraction of a degree lower during the season of cooling. The two curves coincided 
at the annual maximum and minimum. It is consequently sufficient to consider the 
variations of the temperature of the mass as a whole. 

Starting from the minimum of 41° "6 on about April 15th, 1886 (about half a degree 
lower than that of any of the other divisions), the Gareloch reached its maximum of 
54°'l on September 15th, a gain of 12°"5 in 153 days, or at the average rate of 0°*081 
per day. The period and amount of heating were practically identical with those of the 
Channel, and the rate of gain of temperature was twice that of Loch Fyne. The mini- 
mum of 42°*5 was reached on February 28th, 1887, indicating the loss of 11 0, 6 in 166 
days, the rate being o, 070 per day. Here again the rate of change of temperature was 
twice that in Loch Fyne, and slightly greater than in the Channel. The next maximum, 
58°*0, occurred on July 23rd, the duration of heating being only 145 days, more than a 
month less than the time of heating at any other place. The rise of temperature was 
15° "5, and the average rate of heating as much as 0° - 107 per day, being the greatest 
observed in any mass of water in the Area. The shallow Gareloch, on this occasion, was 
naturally enough the division to respond most rapidly to the exceptional solar radiation 
of 1887. The following fall of temperature was prolonged until March 31st, 1888, when 
it reached a minimum of 41 0, 9 after 251 days, the longest period of cooling recorded 
in any division. The total loss of temperature was 16°'l, and the rate of cooling o, 064 
per day, the same as the rate in the Channel. The last maximum observed probably 
occurred on September 15th, and reached 54°-8, a gain of 12 0> 9 in 168 days, again 
the shortest period of heating in the Area. The rate of heating was 0°'079 per day. 

Table XLV. gives concisely the comparative statistics of heating and cooling in the 
four typical divisions of the Area and in Loch Goil. 

The mean duration of heating for the Gareloch, as a whole for the three years 
observed, was 162 days, and for the two periods of cooling 208 days. Taking into 
account the two years for which comparable observations exist, the ratio of the time of 
heating to that of cooling was 160 to 208 days, or 100 : 130. This may be compared 



120 



Mi HUGH ROBERT MILL ON THE 



with 100 : 115 in the Channel, 100 : 100 in the Arran Basin, and 100 : 91 in Loch Fyne, 
and shows that shallowness and exposure to land influences tend to increase the rapidity 
of heating, and probably to retard cooling. The cooling of 1887-88 was evidently 
anomalous, but it may only exaggerate what seems to be a normal disparity. 

The mean rate of change of temperature per day, calculated from the figures in Table 
XLI V., is 0°'074 for the whole mass of water, a change of temperature of 1° requiring 
on the average 13^ days to be effected. The bottom layer of 10 fathoms (10-20 fathoms 



Table XLV. — Period of Heating and Cooling, and Daily Rate of Change of Temperature 

in the Clyde Sea Area. 



Division. 


Warming, 

1886. 


Rate 
per day. 


Cooling, 
1886. 


Rate 
per day. 


Warming, 
1887. 


Rate 
per day. 


Cooling, 
1887. 


Rate 
per day. 


Warming, 

1888. 


Rate 
per day. 


Channel, 


147 days 


0°-090 


171 days 


0°-065 


189 days 


0°-065 


217 days 


0°-062 






Arran Basin, . . 


165 „ 


0°-058 


151 „ 


0°-053 


186 ,, 


0°-046 


199 ,, 


0°-049 






Loch Fyne, . . 


168 ,, 


(T-047 


156 ,, 


0°-039 


206 „ 


0°-037 


184 ,, 


o, 045 


170 days 


0°-033 


Gareloch, . . . 


153 ,, 


0°-081 


166 „ 


0°-070 


145 „ 


0°-107 


251 ,, 


0°-064 


168 „ 


0°-079 


Loch Goil, . . . 


19S „ 


0°-038 


144 „ 


0--040 


160 „ 


0°-058 


210 ,, 


o, 046 


180 „ 


0°-043 



in depth) changed its temperature at the average rate of o, 072 per day, or 1° in 14 days. 
The curve of variation in the rate of change of water-temperature with time which is 
not reproduced brings out the peculiarly prolonged period of falling temperature in the 
spring of 1888. 

The relation of air-temperature to water-temperature is also shown in fig. 46, where 
it is seen that the air-curve cuts the water-curve at the maximum in descending, and 
rather after the minimum in ascending. This proves, as in the case of Loch Fyne, that 
contact with air colder than the surface water arrests the process of heating by 
radiation after the autumnal equinox, while radiation seems to check the loss of heat 
even in contact with colder air after the vernal equinox. It is also remarkable that the 
maximum rate of water-heating occurs nearly a month before the maximum air-tempera- 
ture is reached, while similarly the most rapid cooling occurs a month or so before the 
minimum of air-temperature. This shows that radiation and the other influences 
which produce changes of air-temperature produce the changes of water-temperature 
not consequently but simultaneously, if not previously. 

The air-temperature at Helensburgh (considering monthly means) was above the 
mean temperature of the water of the Gareloch for 154 days in 1886, for 94 days in 
1887, and for 155 days in 1888. The air was colder than the water for 245 days in 
1886-87, and for 250 days in 1887-88. Speaking generally, this gives the air warmer 
than the water for four and a half months from April to August, and colder for the 
remaining seven and a half months. For the two complete seasons included in the years 



CLYDE SEA AREA. 



121 



1886-88, the average period of air warmer than water was for the divisions Channel, 
Arran Basin, Loch Fyne, and Gareloch, 134, 136, 143, and 124 days ; while for air colder 
than water the figures were 237, 223, 219, and 248 days. The rapid heating of the 
Gareloch by radiation brings up the water-temperature so near the air-temperature that 
a short time of air-cooling equalises the two, and stops further heating in the water. 

Interpolating, as in previous cases, probable values for the first three months of 1886 
and the last three of 1888, we get from fig. 47 the data for comparing the mean annual 
temperature of water and air. 

Table XLVI. — Mean Annual Temperature of Air and Water for the Gareloch. 



Year. 



1886 
1887 
1888 
Mean 



I. Air (Mean 
for Area). 



46°-2 
47°-0 
46°-7 
46°-63 



II. Air 

(Helensburgh). 


46°-5 
45°-9 
47°-3 
46°-57 



III. Water 
(Mass). 



47°-4 
48°-7 
47-5 
47°-87 



IV. Water 
(0-5 Fathoms). 



47°-5 

48°-7 
47°-6 
47°-93 



Difference 
(Air II. and 
Water III.). 



Difference 
(Air I. and 
Water III.). 



-° '9 

-2°"8 

- 0°'2 

- i°'3o 



- I - 2 

-i°7 
-o°-8 

- i°'23 



The mean temperature of the air at Helensburgh for 1887 is doubtful, as three 
months had to be interpolated. The early spring of that year was exceptionally cold at 
Helensburgh compared with the other Clyde stations, hence the low annual average. 
The mean, as calculated for the difference between the water and local air, or general 
air-temperature, is practically the same, so that one has some confidence in saying that 
the mass of water in the Gareloch (which is practically at the same temperature as the 
superficial layer) is a degree and a quarter warmer than the air, a somewhat greater 
excess than in the case of the surface water of Loch Fyne. Taking the average of the 
years 1886 and 1887, so as to be comparable throughout, the surface 5 fathoms of water 
in the various divisions were warmer than the air to the following amounts :— Channel, 
1°7 ; Arran Basin, 1°7; Loch Fyne, 1 0> 5 ; Gareloch, 1°'9 (or, taking general air- 
temperature, 1 0, 5). The variation is so slight as to be negligable, and we are justified 
in saying that for these two years the surface layer of 5 fathoms of water in the Clyde 
Sea Area was 1 0, 6 warmer than the overlying air. Considering the mass of water, and 
not the surface layer, we find the Channel and Gareloch practically the same, an excess 
of 1°7, while the excess of the Arran Basin is only 0°'35, and of Loch Fyne 0°-45. 



Loch Goil. 



The physical features of Loch Goil are described in Part L, p. 647. The name is 
applied to the water surface lying within a bar rising to 7 fathoms, which marks off Loch 

VOL. XXXVIII. PART I. (NO. 1). q 



122 DR HUGH ROBERT MILL ON THE 

I J oil from the Dunoon Basin (Lower Loch Long) at the point where Upper Loch Long 
begins. Its length is 5 miles, and average width under f mile. The whole area of the 
water is 3*4 square miles, ami the land drainage is relatively large, being 34 square miles. 
The ratio of water to total drainage area is 1 : 11*07, the smallest ratio for any of the 
sea-lochs, except the Holy Loch, which is simply a bay receiving the drainage of 
Loch Eck, a fresh-water lake. The volume of Loch Goil is 0*037 cubic sea miles, and 
the tidal increment 0*004. Its mean axial depth is 30^ fathoms, and average depth over 
all, 14 fathoms. 

The probable volume of rainfall reaching the loch in an average year is estimated at 
0*02601 cubic sea miles. In 1886-87 it was about 0*01618. 

The average percentage of pure sea-water in the loch is 92*3 

The maximum (in August 1886) was ...... 94*8 

And the minimum (in February 1887) ...... 86*7 

Loch Goil challenges special contrast with the Gareloch, being similar in orientation, 
indeed it is a continuation of the Gareloch in direction ; but the axis is curved instead 
of straight, thus presenting a more complicated outline to up-and-down winds. The 
axis is the same length as that of the Gareloch, the bar is similarly situated and of equal 
depth in both, and the slopes at the head of the lochs have the same angle, but Loch 
Goil is twice as deep as the Gareloch. The surrounding hills are much higher, the 
relative drainage area very much greater, and the normal annual inflow of rain water 
much greater also. In fact, Loch Goil appears to receive its own volume of rain water 
on the average in seventeen months, the Gareloch in thirty-six months. In spite of this 
Loch Goil remains much Salter than the Gareloch, hence there must be a more rapid 
escape of fresh water, or a better supply of salt, the latter being most likely, as the very 
deep water of the head of the Dunoon Basin lies immediately outside the bar. 

The particular points of contrast are thus depth, enclosure by mountains, greater 
salinity, and greater volume of fresh water passing through. 

Comparison must also be made with Loch Fyne, to the Upper Basin of which Loch 
Goil is, on a small scale, very similar, the station at Stuckbeg strikingly resembling that 
at Strachur. Loch Fyne, however, requires in normal years forty-five months in order 
to receive its own volume of fresh water, its drainage area being relatively small. 

Consideration of Loch Goil involves reference to the conditions at the D02; Rock 
station of Dunoon Basin. 

Observations at Dog Rock, Dunoon Basin. — The position of observing was at the 
head of the Dunoon Basin, with Dog Rock bearing N.N.E. 4 cables. The depth is 50 
fathoms, this being the greatest depression of the Dunoon Basin, except that off 
Gantock. To the north-east the water shoals to the sill of Loch Long, to the west it 
shoals to the more pronounced sill of Loch Goil, to the south it shallows gradually. 
See Section 16d., Plate 9 in Part I. The density of the water at this station was as 
follows : — 



CLYDE SEA AREA. 



123 



Mean (11 observations), 

Maximum, 

Minimum, 



Surface. 

1-02280 
102416 
1-01867 



Bottom. 

102463 
1-02504 
1-02420 



The average percentage of pure salt water at the surface was 84 "1, at the bottom 
94*5, iu the whole vertical section 92*8 ; and the assumed percentage for a normal year 
in the vertical section is 92*5, practically the same as that in Loch Goil, as a whole, and 
1 per cent, less than in the Dunoon Basin as a whole. 



Table XLVII. — Temperature Observations off Dog Bock. 



No. 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


Date 


13.4.86 


17.6.86 


5.8.86 


24.9.86 


11.11.86 


12.11.86 


22.12.86 


8.2.87 


25.3.87 


7.5.87 


No. of Points . 


5 


10 


13 


16 


7 


6 


8 


9 


6 


9 


Temp. . 


41-8 


43-9 


47-3 


51-9 


51-2 


51-4 


47-4 


44 4 


43-5 


44-4 


Slope 


+1-9 


+ 5-1 


+ 3-5 


+0-2 


-1-7 


-2-2 


-2-1 


-2-8 


-0-7 


+3-7 


No. 


11 


12 


13 


14 


15 


16 


» 


18 


19 




Date 


14.6.87 


7.8.87 


29.9.87 


15.10.87 


30.11.87 


9.2.88 


1.3.88 


28.3.88 


3.9.88 




No. of Points . 


13 


9 


6 


6 


9 


6 


,! 


6 


9 




Temp. 


46-9 


51-7 


53-3 


52-6 


49-0 


44-9 


441 


42-7 


50-3 




Slope . 


+ 6-8 


+ S-3 


+0-4 


-0-3 


-2-6 


-0-8 


-M 


+ 0-3 


+6-9 





The highest mean vertical temperature observed was 53°'3 in September 1887, the 
lowest was 41 0, 8 in April 1886, a total range of 11 0, 5. The form of the individual 
curves was often interesting. Nos. 4, 13, 14, and 18 were, in view of their "slope," 
practically honiothermic. This was really the case only for Nos. 1 3 and 1 8 in September 
1887 and March 1888, the former the yearly maximum, the latter the yearly minimum. 
In the case of No. 14, and very conspicuously in No. 4, the vertical curve was made up 
of sections of alternately positive and negative slope giving a contorted curve about a 
vertical axis, showing the existence of alternate layers of unmixed warmer and colder 
water (see L in fig. 3, Plate XXIL). Curve 4, in a depth of 50 fathoms, was very fully 
delineated, sixteen points being determined on it. It showed that the layers alternated, 
in increasing thickness, warm, cool, warm, cool, and warm again. The surface tempera- 
ture was 52°*9 (the maximum), the bottom 52°'l ; the minimum, at 29 fathoms, was 
51°-1, and the average of the whole depth 51° -9. 

Nos. 1, 2, and 10 were typical positive paraboloid curves, showing a great range in the 
surface layers and practical homothermicity below. No. 3 is a positive curve showing- 
rapid heating from the surface to 10 fathoms, and beneath that a negative curve of 
nearly uniform gradient to the bottom. 



124 



DR HUGH ROBERT MILL ON THE 



The negative curves here, as in all other stations, are very much less pronounced than 
the positive, the best defined negative paraboloid being No. 15. No. 8 shows a dis- 
turbance on a negative parabolic curve somewhat more complex than No. 3 for a positive, 
but of the same kind. In both the inflection occurs at 10 fathoms, suggesting the action 
on the surface of outflowing water from Loch Goil. 

Curves 5 and G were taken on consecutive days, November 11th and 12th, 1886, and 
the average temperature on the second day seemed to be about 0°'2 higher than on the first, 
although the curves betoken surface cooling. This is partly accounted for by the second 
observation being made in a spot 5 fathoms deeper than the first, these 5 fathoms being 
occupied by warmer water. Both curves show a sub-surface maximum, followed by a 
fall of temperature, and if more points on the curves had been ascertained they might 
show a closer concordance. 

Out of the nineteen curves it is interesting to notice that no less than nine show 
mixed slopes to a greater or less extent ; but from this station alone it does not appear 
that change of slope within the curve is a normal feature of seasonal range. The position 
of the Dog Rock Station is unique in the Area, as it is a deep depression at the junction 
of three long narrow channels of different depth, salinity, and accessibility to sea 
water. Consequently, it is peculiarly subject to variations in the slope of its temperature 
curve similar to those at ( )tter I. Kilfinan. 

Observations at Loch Goil Mouth. — The observations made at the mouth of Loch 
Goil were intended to be on the deepest part of the sill or bar which separates it from 
the Dunoon Basin. The depth of observation usually varied from 9 to 12 fathoms, 
although it is probable that a line, with 8 fathoms as its maximum depth, runs across the 
mouth of the loch. The crest of the sill is narrow, and no leading marks were found to 
enable its position to be fixed exactly while observing. The station lay on the line 
between the curve of Corryn on the chart and Swine's Hole, where the channel 
was \ of a mile wide. 

No salinity observations were made. 

Table XLVIIL — Temperature Observations at Loch Goil Mouth. 



No 


1 


■2 


3 


4 


5 


6 


7 


8 


9 


Date .... 


5.8.86 


8.2.87 


25.3.87 


7.5.87 


14.6.87 


7.8.87 


29.9.87 


30.11.87 


10.2.88 


Xo. of Points . 


4 


3 


3 


G 


6 


3 


2 


6 


3 


Temperature 


49-4 


43-5 


42-8 


46-5 


49-4 


55-9 


53-4 


47-3 


45-0 


Slope .... 


+ 33 


-2-8 


-0-8 


+ 2-4 


+ 2-5 


+ 2-8 


+ 0-3 


-23 


-0-2 



The curves were, as a rule, nearly straight lines, occasionally showing very well-marked 
positive or negative slope. 

Observations off Carrick Castle. — Observations were made twice off Carrick Castle, 
2 of a mile distant from the station at the mouth of the loch, in a depth of 25 fathoms. No 






CLYDE SEA AREA. 



125 



salinity observations were made. They were on March 25th and September 29th, 1887. 
Six points on the curve were fixed on each occasion. On the former the mean temperature 
was 43°'6, and the slope — l° - 6 ; on the latter the mean temperature was 51°'3, and the 
slope +4°"5. Both curves are S-shaped, one positive and one negative. They betoken 
a division of the water into three layers, a surface and a bottom one of nearly uniform 
temperature, and an intermediate zone of rapid change of temperature. 

Observations at Stuckbeg. — At this point observations were made at the deepest part 
of Loch Goil in mid-channel, about two-thirds of the way from the mouth to the head of 
the loch. The depth is 47 fathoms, and the bed of the loch is exceptionally steep (see 
Section 8b., Plate 7 in Part I.). The density of the water was as follows : — 



Mean (10 observations;, 

Maximum, 

Minimum, 



Surface. 

102293 
102441 
102036 



Bottom. 

1-02452 
102471 
102410 



Average percentage of pure sea-water at the surface 86*0, at the bottom 93*9, in 
vertical section 92*6, and probable mean for normal year 9 2 2 per cent. This station 
was a little Salter on the surface and a little less salt at the bottom than Dog Rock, the 
average being practically the same. 



Table XLIX. — Temperature Observations off Stuckbeg. 



No. 


1 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


Date 


13.4.86 


17.6.86 


4.8.86 


5.8.86 


24.9.86 


12.11.86 


22.12.86 


8.2.87 


25.3.87 


7.5.87 


14.6.87 


No. of Points 


5 


10 


4 


10 


10 


14 


9 


9 


9 


9 


19 


Temperature . 


41-8 


434 


45-4 


45-6 


47-3 


48-4 


47-5 


45 5 


43-9 


44-5 


46-2 


Slope . 


+ 1-5 


+ 5-5 


+ 6-9 


+ 7-9 


+ 7-9 


+ 4-5 


-1-5 


-4-7 


-0-6 


+ 3-2 


+ 6-0 


No. 


12 


13 


14 


15 


16 


17 


18 


19 


20 


21 




Date 


7.8.87 


29.9.87 


15.10.87 


30.11.87 


9.2.88 


1.3.88 


28.3.88 


15.8.88 


3.9.88 


23.10.8J 


» ... 


No. of Points 


9 


8 


6 


12 


6 


6 


6 


6 


10 


6 




Temperature . 


49-8 


50-3 


49-9 


49-1 


46-0 


44-1 


433 


46-3 


47-0 


47-0 




Slope . 


+ 11-7 


+ 6-3 


+ 3-4 


-2-9 


-10 


+ 0-2 


+ 0-3 


+ 8-9 


+ 10-5 


+ 4-8 





It is unnecessary to analyse the temperature curves in detail. As in all other places 
of observation, they approached a homothermic state at the annual minimum ; the slope 
of the curves was positive during the months of heating, and negative during those of 
cooling. Unlike the Gareloch, however, there is no tendency to assume a homothermic 
state at the annual maximum, the transition from positive to negative slope being 



1 26 



DR HUGH ROBERT MILL ON THE 



effected, as in Loch Fyne, by a transition period of mixed slopes. When the Stuckbeg 
curves (figs. 19 to 21, Plate VII.) are compared with the upper 44 fathoms of the Loch 
Fyne curves (figs. 16 to 18), they are seen to be very similar indeed. Curves of the 
same date are numbered and coloured alike, and the fact appears that the conditions 
during the three years of observation varied similarly in both basins. 







Table L 


. — Typical Vertical T&m/peratv/re Curves at Stuckbeg. 




35 


1886-87. 




1887-88. 




1888. 


Reference 




Time 


Reference 




Time 


Reference 




Time 


> 
U 


Table 


Date. 


Interval. 


Table 


Date. 


Interval. 


Table 


Date. 


Interval. 


O 
I 


XLIX. 




Days. 


XLIX. 




Days. 


XLIX. 




Days. 


1 


April 13 




9 


Mar. 25 


45 


18 


Mar. 28 


48 


II 


2 


June 17 


65 


10 


May 7 


43 








III 


3-4 


Aug. 4-5 


48 


11 


June 14 


38 


19 


Aug. 15 


140 


IV 


5 


Sept. 24 


51 


13 


Sept. 29 


107 


20 


Sept. 3 


19 


V 


6 


Nov. 12 


49 


15 


Nov. 30 


62 


21 


Oct. 23 


50 


VI 


7 


Dec. 22 


40 














VII 


8 


Feb. 8 


48 


16 


Feb. 9 


71 









It is noteworthy that in these curves the point of rapid inflection is almost always at 
20 fathoms of depth, both for positive and negative slopes, and below that depth there 
is an approximation to homothermic change. The curves as a whole bear a considerable 
resemblance to those of the Arran Basin. The homothermic character of the curves 
poiuts to a more thorough mixture of the water of the loch than holds good for Loch 
Fyne, but yet the seasonal phase was retarded at the bottom almost as much as in Loch 
Fyne, the bottom minimum occurring in late spring, and the bottom maximum in early 
spring, the rise of temperature from minimum to maximum occupying approximately nine 
months, and its fall to the next minimum requiring only three. 

In 1886-87, which may be taken as an approach to a normal year, the range of tem- 
perature at the surface was about 14°, at 10 fathoms 9°'5, at 20 fathoms (where the 
abrupt change in the character of the curves begins) 6° "5, and below this depth to the 
bottom the seasonal amplitude remained practically the same, thus differing sharply from 
the condition in Loch Fyne. The retardation of the temperature phase at the bottom 
makes the temperature region of Loch Goil still more unlike that of the Arran Basin. 

The Time-depth diagram (fig. 4, Plate III.) shows the condition of temperature-change 
at all depths at Stuckbeg. It very closely resembles that for Loch Fyne, so far as the 
depths correspond. The diagonal run of the isotherms is as well-marked here as in Loch 
Fyne. In 1886 it showed that the surface was above 50° from July 12th to November 6th, 



CLYDE SEA AREA. 127 

the isotherm of 50° reaching its greatest depth, 18 fathoms, on November 12th, having 
a much more marked diagonal trend than in Loch Fyne. The rate of descent also was 
far slower, 123 days being required for 18 fathoms, contrasted with 110 days for 105 
fathoms at Skate Island, and 92 days for 23 fathoms in Loch Fyne. In 1887 the surface 
was above 50° from May 10th to October 25th, and the temperature of 50 c reached 
its greatest depth, 20 fathoms, on November 28th, again long after the date when the 
isotherm had passed out at the surface during the winter cooling. On this occasion 
202 days were required to carry the isotherm down to 20 fathoms (although 92 clays had 
taken it to 19 fathoms), compared with 123 daj^s for 30 fathoms in Loch Fyne, and 123 
days for 60 fathoms at Skate Island. In 1888 the rather incomplete observations 
showed that the surface was above 50° from June 24th until October 23rd, and the 
isotherm reached its maximum depth of 11 fathoms on September 3rd, after 71 days, 
compared with 31 days for 12^ fathoms in Loch Fyne. 

The time-depth diagram also serves to measure the retardation of the seasonal phase. 
In 1886 the surface maximum occurred on September 25th, while the bottom maximum 
was delayed until January 15th, 1887, an interval of 112 days, or 285 days after the pre- 
vious bottom minimum. The retardation was at the rate of 2*5 days per fathom, com- 
pared with 2*8 days per fathom in Loch Fyne. The bottom minimum occurred on 
April 15th, only 60 days after the surface minimum, and 88 clays after the bottom 
maximum. The maximum of 1887 occurred 241 days later, on December 12th, about 
120 days after the surface maximum ; on this occasion the retardation per fathom was 
2*7 days, compared with 2*3 days for Loch Fyne. The next bottom minimum came 
after 109 days apparently, probably simultaneously with the surface minimum. The 
average retardation of the maximum for the two periods was 116 clays, or practically 
four months, as compared with six months in Loch Fyne, and two months at Skate 
Island. The average ratio of the times of heating and cooling at the bottom was 
263 : 84 days, or roughly, 3 to 1. 

Observations at Lochgoilhead. — At this place observations were made a little to the 
south of the steamer pier in mid-channel, just at the commencement of the abrupt rise of 
the loch-bed at the head. The depth was about 25 fathoms, but observations were occa- 
sionally made opposite the pier where the depth was from 12 to 10 fathoms. 

The density of water was as follows : — 

Bottom. 
1-02440 
102465 
102400 

The average percentage of pure sea- water at the surface was 8 2 "6, at the bottom 93*8, 
and in vertical section 91*9. The probable normal value in the vertical section was 91 '4. 
The distribution of temperature resembled on the whole that at Stuckbeg, with the 
differences always associated with shallower water and a position close to the upper end 
of a loch basin. 





Surface. 


Mean, 9 observations, . 


102236 


Maximum, 


102427 


Minimum, 


101797 



128 



DR HUGH ROBERT MILL ON THE 



Temperature Sections of Loch God. — The deep basin of Loch Goil affords an 
interesting contrast to the similarly formed but much shallower basin of the Gareloch, 
the main difference appearing in its more sluggish temperature transactions, and, except 
at the yearly minimum, its generally lower temperature. The seventeen sections (figs. 1 
to 17, Plates XVII. and XVIII.) are drawn on the same scale as those of the Gareloch, 
and are different in the ratio of horizontal to vertical scale from those of Loch Fyne. 



Table LI. — Temperature Observations at Lochgoilhead. 



No. ... 


] 


2 


3 


4 


5 


6 


7 


8 


9 


10 


11 


12 


13 14 


15 


16 


Date . . . 


17.6.86 


4.8.86 


24.9.86 


11.11.86 


12.11.86 


22.12.86 


25.3.87 


7.5.87 


14.6.87 


7.8.87 


29.9.87 


30.11.87 


10.2.88 


1.3.88 


28.3.88 


3.9-80 


No. of Pts. . 


12 


10 


7 


6 


1 


8 


6 


6 


7 


6 


4 


6 


6 


6 


3 


5 


Temp. . . 


44-5 


47-2 


48-4 


50"2 


49-6 


471 


44-1 


45-8 


50-1 


52-5 


54-0 


48-1 


45-7 


44-5 


43-1 


Slope . . 


+ 4-9 


+ 6-7 


+ 6-4 


+ 0-2 


+ 2-2 


-1-5 


-1-0 


+2-4 


+ 1-6 


+ 9-4 


+ 1-3 


-1-6 


-0-4 


+ 0-3 


-0-5 


+ 4'2 



Section I., 13th April 1886. — Observations at Dog Rock and Stuckbeg only. Flood- 
tide. The temperature of the mass of water below 4 fathoms sank from 42° to 41°'5. 
The top layer, traversed by parallel isotherms, was warmed to 44 0, 4 and 45°. No data 
were afforded for determining circulation. There was no wind. 

Section II, 17 th June 1886. — Three sets of observations were made. The isotherm 
of 46° ran horizontally at 4 fathoms. Below that there was a slight landward dip and 
fall of temperature to under 42° ; above it probably a seaward dip, but want of an 
observation at the mouth makes this uncertain. The surface water grew steadily cooler 
as the loch was ascended. The tidal phase varied, and the wind was light from N.W. 
No sufficient indications of circulation were shown. 

Section III, 5th August 1886. — Four stations. The isotherms were numerous, of 
slight and various inclination, practically horizontal. That of 44° ran at 27 fathoms instead 
of 12, as in June. Surface layers were warming rapidly, and the surface was growing 
cooler landward. The tide was at the beginning of flood, and the wind light from the 
south-east. The isotherms showed no disturbance on the bar. The deep water outside 
was practically homothermic at 49° from the bar sill to the bottom, while inside it sank 
to 43° "1 ; the bar thus shutting off cold water in the loch from water 5° warmer at the 
same depth outside. 

Section IV., 2Uh Septemher 1886. — Three stations ; none at mouth. The isotherm 
of 45° ran at 25 fathoms instead of 19 fathoms, as in August. The bottom temperature 
inside was 44° - 2, while outside it was practically uniform to the bottom at 52°, a difference 
of nearly 8°. Isotherms showed a very slight seaward dip, with tide at second half of 
ebb, and there was no wind. The fall of temperature was most rapid just below the 
level of the sill, there being a Sprung schicht at 17 fathoms. Above that the temperature 
was practically continuous with that outside. 



CLYDE SEA AEEA. 129 

Section V., 12th November 1886. — Three stations. Outside the sill a uniform rise 
of temperature occurred from surface to bottom, which was at 52° '2. Inside, the water 
o-rew warmer from 49° on the surface to 51° at sill-level, thence there was a steady fall 
(most rapid as in IV. in a Sprung schicht about 17 fathoms) to 45°"8, i.e., 8°'4 lower than 
outside. The isotherm of 46° had moved from 19 fathoms in IV. to 36 fathoms. On the 
whole the isotherms showed a very slight seaward dip, a little masked by cooling at the 
head of the loch. The tide was in the first quarter of flood when the observations in 
rhc loch were made, and a little past high-water when the sounding was made outside. 
There was no wind. 

Section VI, 22nd December 1886. — Three stations. Outside the bar a slight rise 
of temperature occurred with depth, from 45°'6 to 48°, with a slight minimum a little 
before the bottom. Inside, there was the same rise to 20 fathoms, at 25 fathoms a slight 
maximum of 48°'0, and then a fall to 47°'6 on the bottom. There was a slight seaward 
dip of the upper isotherms, but they were, as a whole, practically horizontal. The tide 
was in the first quarter of ebb, and the wind was fresh from the north, with rain. There 
was thus a surface current flowing out of the loch. 

Section VII., 8th February 1887. — Three observations were made, viz., at Dog Rock, 
the Mouth, and off Carrick Castle, floating ice stopping farther work. The isotherms 
were horizontal, except for the increasing cold of the surface landward. Outside, 45° was 
found at 34 fathoms, and 45°'3 at the bottom ; inside, 45° occurred at 10 fathoms, and 
47°"2 at the bottom, the maximum having thus worked its way fully down, and the bar 
now serving to hold back warm water in the loch. The fall of temperature was very 
rapid at the surface, falling from 39° to 44° in 2|- fathoms. The tide was at the first half 
of ebb, and the wind was imperceptible. 

Section VIII, 25th March 1887. — Five stations were visited, the observations being 
very complete. The surface isotherms showed a general seaward dip. It was flood-tide, 
and the wind was fresh from the north, blowing against it. Outside, the temperature rose 
from 42° "8 on the surface to 43° - 6 on the bottom ; inside, below the sill it was practically 
constant at 44°, although an ill-defined area of slightly higher temperature appeared. 
Compared with No. VII., it would seem that the superficial layers remained at nearly 
constant temperature, while the mass below the sill had cooled down on the bottom from 
47°'2 or more to 43" "9. This may be due to the mixing power of up-loch winds ; but at 
the time of observation the down-loch wind appeared to be banking the cold surface 
water against the inner side of the sill of the basin and causing a partial updraught at 
the head. 

Section IX., 7th May 1887. — Four stations were visited. The temperature inside 
below 10 fathoms was practically unchanged since No. VIII. The upper layers showed 
rapid heating. The isotherms were practically horizontal, and the bar might have been 
removed without sensibly disturbing the temperature distribution, that inside and outside 
being alike. It was early flood-tide, and the wind was very light from south and west. 

Section X., lUh June 1887. — Observations were made at four stations. There was 

VOL. XXXVIII. PART I. (NO. 1). R 



130 DR HUGH ROBERT MILL ON THE 

.1 slight seaward clip of the upper isotherms, and a slight landward dip of the lower, with 
ebb-tide, and wind very light from west and south. Rapid heating of the surface layers 
was in progress, the surface being above 49° ; a steady fall outside brought the 
temperature to 47° at 15 fathoms, and 45°"2 at the bottom. A fall to 45° at 15 
fathoms took place inside, and from that point the temperature was practically uniform 
to the bottom. The fan-like spread of isotherms against the upper end of the loch 
strongly suggests the effects of an on-shore wind on the west coast, while the arrangement 
outside suggests the opposite action. 

Section XL, 7th August 1887. — Four sets of observations were made. This was 
the section showing maximum temperature, and the isotherms were almost perfectly 
horizontal, with tide at the beginning of ebb and the wind varying from a light 
westerly breeze to calm. Outside, there was a gradually decreasing rate of fall of 
temperature from 58°*2 on the surface to 49° on the bottom. Inside, there was a rapid 
fall (equal with that outside to the edge of the bar) from 58°'6 to 47° at 23 fathoms, 
and then a very gradual fall to 45° "4 at bottom. Thus the bottom temperature had 
risen half a degree and the surface 6° since No. X. 

It is interesting to note that in August 1886 the distribution of temperature was 
similar, and although the degree was lower, the difference of 4° between the bottom 
temperatures on the two sides of the barrier was the same. 

Section XII., '29th September 1887. — On this occasion there were five stations, 
observations being exceptionally complete. A general fall of temperature had taken 
place in the upper layers since No. XL The temperature was unchanged at 15 fathoms, 
and below that it had risen. Outside the bar the surface had cooled 4 c- 2, and the 
bottom warmed 4°'l ; inside, the surface had cooled 4° - 3, and the bottom warmed only 
2°'l. Outside, the water was now practically homothermic at 53°"5 ; inside, it sank 
from 54°-3 to 47°-5. 

The isotherms showed a strong landward dip throughout the whole depth. 
There was a very well marked banking-up of warm water at the head, and a distinct 
uprising of cold water just inside the bar. The water was evidently being driven in, in 
spite of the tide, which was in the first half of ebb ; a strong breeze was blowing from 
E.N.E. As in the last and many previous cases, the isotherms about 18 fathoms lay 
close and parallel, indicating the plane of junction between warm upper and cool lower 
layers The easterly component of the wind would account for the homothermic water 
of the Dunoon Basin being driven into Loch Goil, and thus give rise to the thick 
warm layer deepening toward the head. 

Section XIII. , Wth November 1887. — Four stations were visited. The isotherms on 
the whole were horizontal. The tide was in the last half of flood, and the wind both light 
and variable. Continuous cooling of the upper layers had gone on, and outside the bar 
the whole depth had cooled down equally. Inside the bar, cooling had taken place to 20 
fathoms, where the temperature was the same as in the previous month, and below that 
depl li I here was warming. At the bottom the water had reached the maximum temperature 



CLYDE SEA AREA. 131 

for tlie year, 49°'4. Outside, the surface had cooled 11°"5, and the bottom 3°7, since No. 
XII. ; inside, the surface had cooled 9°1, and the bottom had warmed 2°. The maximum 
temperature inside was 50° at 20 fathoms, half a degree warmer than the bottom, and 
4° '8 warmer than the surface. 

Section XIV., Februa/ry 9th-l0th, 1888. — Four stations were examined. The 
upper layers were distinctly warmer than in No. XIII., but the bottom was 4° '3 colder 
outside and 3° "2 colder inside than on the former occasion. Below the level of the bar 
the water outside was homothermic at 45°, that inside at 46°. The isotherms showed 
a strong seaward slope, indicating a mixture and out-flow of the surface water. Ebb 
tide preponderated, and the wind was W.N.W., or in the main down-loch, and squally. 
This section may be profitably compared with No. XII. for the relation of dip of 
isotherms to wind. 

Section XV., March 1st, 1888. — Three stations only were studied. The temperature 
varied only from 44° '0 to 44° *9 inside, so that no evidence as to circulation was afforded. 
The surface (whole depth outside) had cooled down 0°7 ; the bottom inside had cooled 
2°. This very rapid cooling of the bottom layers, and the general equalisation of 
temperature throughout the basin, is characteristic of the spring minimum, but was more 
marked in 1888 than in 1887. 

Section XVI., March 28th, 1888. — Three stations were again visited. Slight general 
cooling had occurred. Outside, the surface temperature was 43° (the same as in No. 
XV.), the bottom 42°*6, or 0°*7 colder. Inside, the surface temperature was 43 0- 3, the 
bottom 43°*1, the maximum, a little under 44°, occurring at 10 fathoms. No evidence 
as to circulation appeared. 

Section XVII, September 3rd, 1888. — This was the last trip, and included three 
stations. The general distribution of temperature in its main features resembled that 
of the two previous Septembers, only outside the bar the surface was warmer and 
the bottom water colder than in former cases. The isotherms were appreciably 
horizontal. The fall of temperature from 56° on the surface to 51° at the level of the 
sill was uniform over all. Outside, the further fall to 48° '2 on the bottom was very 
gradual ; while inside, the fall to a little under 44° was rapid and almost perfectly 
uniform. The minimum occurred at 35 fathoms, the bottom being a fraction of a degree 
warmer. As in both the previous Septembers, the bottom temperature inside was 4° 
lower than that outside. 

From reasoning based on the great rainfall of the Loch Groil catchment basin, and 
the relatively high and constant salinity of the water in the loch, it is plain that there 
must be a double circulation always in operation, the flowing out of fresher and the 
flowing in of Salter water. It is surprising that the isotherms show so little evidence of 
this circulation, especially as the contrast of temperature on the two sides of the bar is 
usually sharp. The only way of explaining this is that the circulation must be mainly 
effected by the tides, working continuously but so gradually that the small quantity of 
salt water brought in accommodates its temperature to that of the mass of the water in 



132 



DK HUGH ROBEUT MILL ON THE 



the basin. The constancy of the Sprungschicht at 18 fathoms, as shown in the sections, 
and the striking change in the form of the curves of vertical distribution of temperature 
at 20 fathoms, indicate that the circulation takes place mainly in the upper half of the 
water ; but the homothermic change of the lower half tells us that there is circulation 
regularly in operation to the bottom. The retardation of the maximum is proof enough 
that this circulation is restricted and gradual in its operation. 

The average temperature of each section was ascertained by measurements on the 
section in the manner explained on p. 10. Tables LII. and LIII. give the weighted 
mean temperature of each section, and the estimated mean temperature of each slice of 
1 fathoms, as well as the rate of change of temperature between successive sections. 
The figures so tabulated arc rendered graphically in the curves of fig. 48, Plate XXXI. 
The air- temperature given in fig. 48 is the mean of that at Helensburgh and Callton 
Ator, this probably representing some approximation to the actual air-temperature over 
the loch itself. 



Table LII. — Mean Temperatures at various Depths in Loch Goil. 



Trip. 


Date. 


Interval. 
Days. 


Mean Temp. 

of Mass 
"Weighted. 

41-84 


Diff. 




Mean Temperatures of Layers. 


0-10 fms. 


10-20 fms. 


20-30 fms. 


30-40 fms. 


I. 


13.4.86 




42-18 


41-60 


41-55 


41-50 


II. 


17.6.86 


65 


44-46 


+ 2-62 


46-23 


43-71 


42-40 


42-00 


III. 


5.8.86 


49 


47-12 


+ 2-66 


49-75 


45-98 


44-15 


43-27 


IV. 


24.9.86 


50 


48-94 


+ 1-82 


51-64 


48-43 


45-06 


44-30 


V. 


12.11.86 


49 


49-34 


+ 0-40 


50-50 


49-87 


46-86 


46-10 


VI. 


22.12.86 


40 


47-05 


- 2-29 


46-35 


47-38 


47-86 


47-90 


VII. 


8.2.87 


48 


45-11 


-1-94 


43-60 


45-70 


46-90 


47-32 


VIII. 


25.3.87 


45 


43-80 


-1-31 


43-45 


44-13 


44-00 


43-95 


IX. 


7.5.87 


43 


44-94 


+ 1-14 


46-03 


44-20 


43-97 


43-92 


X. 


14.6.87 


38 


47-34 


+ 2-40 


49-62 


45-99 


45-05 


45-00 


XI. 


7.8.87 


54 


52-34 


+ 5-00 


56-00 


51-52 


47-30 


45-92 


XII. 


29.9.87 


53 


51-74 


-0-60 


53-52 


51-49 


49-21 


48-11 


XIII. 


30.11.87 


62 


4S-60 


-3-14 


47-35 


49-39 


49-85 


49-60 


XIV. 


9.2.88 


71 


45-70 


-2-90 


45-35 


45-90 


46-05 


46-15 


XV. 


1.3.88 


21 


44-10 


-1-60 


44-19 


44-05 


44-00 


44-03 


XVI. 


28.3.88 


27 


43-42 


-0-68 


43-33 


43-50 


43-50 


43-48 


XVII. 


3.9.88 


... 


50-05 




53-34 


49-10 


45-95 


44-10 



These curves of temperature at different depths present much similarity to those of Loch 
Fyne (fig. 41, Plate XXX.). The air-curve is practically the same, though the maxima for 
188G and 1888 are rather higher than for Loch Fyne. The curve of mean temperature of 



CLYDE SEA AKEA. 133 

the surface layer of 5 fathoms is of considerably greater amplitude, and a little earlier in 
phase than that for Loch Fyne, corresponding more closely with that for the G-areloch 
(fig. 47, Plate XXXI. ). In 1886 the curve is so flat, and the apparent maximum so late 
and low, that it seems possible that the true maximum fell between the dates of observa- 
tion. On the other hand, the rate of heating was less throughout than in other years, and 
it may be that the exceptionally low minimum temperature of the spring gave rise to the 
retardation. It is difficult, however, to account for the rate of surface heating being less in 
Loch Fyne, whereas in subsequent years it was greater. Probably the fact was due to 
local causes, such as the direction and force of the wind, or to the amount and temperature 
of the rainfall entering the loch, and it is, unfortunately, impossible to obtain data for 
these conditions. 

The bottom layer of Loch Goil gave a curve corresponding closely in form and 
irregularities with that of the layer between 30 and 40 fathoms in Loch Fyne ; but in 
1886 its range was less, on account of a lower maximum, and the period of the maximum 
was both in 1886 and 1887 fully a month later than that of water at the same depth in 
Loch Fyne, occurring as it did about the end of December. The retardation was not 
so great as for the bottom water of Loch Fyne. but approached it sufficiently to show 
that the steepness of the sides of a basin has a great deal to do with the temperature 
regime of its water, and that depth alone does not condition the manner and rate of 
change. The maximum of the bottom layer was retarded about 180 days after the air 
maximum in 1886, and 150 days in 1887, comparing with 126 and 120 days for the 
retardation of the maximum at the same depth (30-40 fathoms) in Loch Fyne. In the 
two years the rate of sinking of the maximum was very nearly the same ; for the 
maximum temperature at 20 fathoms it was 60, at 25 fathoms 90, and at 40 
fathoms 105 days later than at 5 fathoms, while in Loch Fyne the retardation was 20, 
30, and 60 days respectively ; the average retardation at the bottom being only 105, 
although the depth is twice as great as in Loch Goil. Thus the isolation of the Loch 
Goil basin is twice as efficient as that of Loch Fyne. 

Considering the variations in temperature of the mass of water in Loch Goil, it is 
found that from the minimum of 42° to the maximum of 49°"6 in 1886, the time was 
198 days, and the rate of heating only o, 038 per day. This was a longer period of 
heating by 30 days than in Loch Fyne, and by 45 days than in the Gareloch, while the 
rate of heating was less than half that of the Gareloch, and less by one-quarter than that 
of Loch Fyne. The following cooling period was 144 days, when a minimum tempera- 
ture of 43 0, 8 was reached, the daily rate of cooling being 0°*040. This was practically 
the same rate of cooling as for Loch Fyne, but the time was 12 days less, and 22 days 
less than the Gareloch. In 1887 the maximum was 53°'0 after 160 days' heating at 
the rate of 0°*058 per day, nearly as much longer and slower than the Gareloch as it 
was shorter and quicker than Loch Fyne. The succeeding minimum of 43° '4 was 
reached by an average cooling of 0°*046 in 210 days, the rate being the same as in Loch 
Fyne, but the time 26 days longer, although 41 days shorter than in the Gareloch. 



134 



DR HUGH ROBERT MILL ON THE 



The period of warming in 1888, up to probably 51°*2, was about 180 days, at the rate 
of o, 043 per day. The average time of heating for the three years was 179 days in 
Loch Groil, and the average time of cooling for the two seasons 177. In 1888 it 
happened curiously enough that the period of heating was the mean of the two earlier 
years, so that for the two years comparable for the whole Area the ratio of time of 
heating to time of cooling was 179: 177 or 100 : 99. Taking 100 as representing the 
duration of heating, the duration of cooling in the different divisions was : — 

Gareloeh. Channel. Arran Basin. Loch Goil. Loch Fyne. 

130 115 100 99 91 

J udged in this way, the two divisions, where the surface-temperature is always close to 
the average temperature of the water, would seem to heat up more quickly than they 



Table LIII. — Average Change of Temperature per diem in Loch Goil. 



J )ate. 


No. of 
Days. 


Mass of Water. 


0-10 Fathoms. 


10-20 Fathoms. 


20-30 Fathoms. 


30-40 Fathoms. 


17.6.86 


65 


+ 0-040 


+ 0-062 


+ 0-032 


+ 0-013 


+ 0-008 


3.8.86 


49 


+ 0-054 


+ 0-072 


+ 0-046 


+ 0-036 


+ 0-026 


24.9.86 


50 


+ 0-036 


+ 0-038 


+ 0-049 


+ 0-018 


+ 0-021 


12.11.86 


49 


+ 0-008 


- 0-023 


+ 0-029 


+ 0-037 


+ 0-037 


22.12.86 


40 


-0-057 


-0-104 


- 0-062 


+ 0-025 


+ 0-045 


8.2.87 


48 


-0 040 


-0-057 


-0-035 


- 0-020 


-0012 


25.3.87 


45 


- 0-029 


o-ooo 


-0036 


-0-056 


-0-077 


7.5.87 


43 


+ 0-027 


+ 0-060 


+ o-ooo 


-0 000 


-0000 


14.6.87 


38 


+ 0-063 


+ 0-095 


+ 0-047 


+ 0028 


+ 0-028 


7.8.87 


54 


+ 0-093 


+ 0-118 


+ 0-102 


+ 0-042 


+ 0-017 


29.9.87 


53 


-0-011 


-0-047 


o-ooo 


+ 0-036 


+ 0-041 


30.1 1.87 


62 


-0-051 


-o-ioo 


- 0-034 


+ 0-010 


+ 0-024 


9.2.88 


74 


-0-040 


-0-028 


- 0-048 


-0-053 


-0-048 


1.3.88 


21 


-0-076 


-0-055 


- 0088 


-0-098 


-0-101 


28.3.88 


27 


- 0-025 


-0-003 


- 0-002 


-0-002 


- 0002 


Mean Heating . 




+ 0-046 


+ 0-074 


+ 0-051 


+ 028 


+ 0-027 


No. of Cases 




7 


6 


6 


9 


9 


Mean Cooling . 




-0041 


-0052 


- 0-043 


- 0046 


- 0-048 


No. of Cases 




8 


8 


7 


5 


5 


Mean Change . . . 


0-043 


0-061 


0-047 


0-034 


0-034 



CLYDE SEA AREA. 



135 



cool, while those in which depth and isolation retard temperature changes gain and lose 
heat, on the whole, at the same rate ; or, as in the case of Loch Fyne, cooling is more 
rapid than heating. The fact that the two years, 1886 and 1887, were very unlike 
in their thermal relations deprives these averages of any general application in the case 
of Loch Goil. 

The rate of change of temperature in fractions of a degree per day is shown in 
Table LIIL, and, together with the same data for Loch Fyne, graphically in fig. 42, Plate 
XXX. The mean daily change of temperature for the whole mass is o, 043, or a change of 
one degree in 23 days, as compared with one degree in 1 3| days for the Gareloch, and in 
25 days for Loch Fyne. For the surface layer of 10 fathoms it is 0° - 061, or one degree in 
16^ days, compared with 19 for Loch Fyne. From 10 to 20 fathoms the rate of change 
was the same in Loch Goil and Loch Fyne ; from 20 to 30 fathoms the Loch Fyne change 
was slightly greater, and from 30 to 40 fathoms both were alike, 30 clays being required 
for a change of one degree. 

As in all other cases, the descending curve of air-temperature cut the curve of surface- 
temperature at the maximum, and also cut the curve of mass-temperature at its 
maximum a month or so later. In each case the ascending air-curve cut the others 
about 10 or 15 days after their minimum. 

The air was warmer than the surface layer of 5 fathoms for 172 days in 1886, 104 
in 1887, and 132 in 1888, averaging 136 days for the three periods ; while it was colder 
than the surface layer for 224 days in 1886-87, and 248 in 1887-88, an average of 236 
days. The average of the two seasons is 138 days of air warmer, and 236 days of air 
colder than surface water, or 4^ months to 7 J. This was exactly intermediate between 
the data for the Gareloch and Loch Fyne, in the former the period of warmer air being- 
shorter, and in the latter longer than in any other division. 

Table LIV. — Mean Anmial Temperature of Air and Water for Loch Goil. 



Year. 


I. Air. Mean 
for Area. 


II. Air. Mean 
for Helensburgh 
and Callton Mor. 


III. Water. 
0-5 Fathoms. 


IV. Water. 
Mass. 


Difference 
Air II. and 
Water III. 


Difference 
Air II. and 
Water IV. 


1886 
1887 
1888 
Mean 


46-2 
47-0 
46-7 
46-63 


46-0 
46-4 
46-9 
46-43 


47-1 
48-9 
47-9 
47-97 


45-7 
47-9 
47-1 
46-90 


— IT 

-2-5 

— I'O 

-i "54 


+ o- 3 
-i'5 

— 0'2 

-o"47 



By interpolating probable values for the first three months of 1886 and the last 
three months of 1888 the curve (fig. 47, Plate XXXI.) gives the means of estimating the 
average annual temperature of the three years. This is given in Table LIV. 

The average temperature of the surface layer for the whole time of observation was 



136 DR HUGH ROBERT MILL ON THE 

the same in Loch Goil and the Gareloch, and rather less than half a degree higher than 
the surface layer in Loch Fyne. The temperature of the mass of the water in 
Loch Goil was on the average half a degree higher than in Loch Fyne. The mean 
annual temperature of the surface layer in Loch Goil was 1°"5 higher than the air- 
temperature for the years 1886-87, the same as for Loch Fyne, and about quarter of 
;i degree less than for the other divisions. The mass of water in Loch Goil, like that in 
Loch Fyne, averages 0°"4 higher than the air. 

All the observations show that, proportionally to its depth, temperature changes are 
more restricted in Loch Goil than in Loch Fyne, with which alone it can be compared, 
and its isolation from oceanic influences appears to be more complete. 

Loch Strivan. 

Loch Strivan is an example of a loch basin imperfectly shut off from the Arran and 
Dunoon Basins by the broad and not very shallow Bute Plateau, and connected with 
the Arran Basin also, so far as superficial water is concerned, by the narrow and tortuous 
channel of the Kyles of Bute. 

The loch is described in its physical features in Part I. p. 648. It differs from the 
other loch basins mainly in having no sharply-defmed bar, and in its breadth 
diminishing uniformly from its mouth to the head. The section along the axis of 
the loch given in Part I., Plate 8, No. 12, brings out its peculiar form, the deepest 
channel across the Bute Plateau being 25 fathoms, while the greatest depression of Loch 
Strivan is only 42. For the steepness of its hill-slopes this loch may be compared to 
Loch Goil or the upper basin of Loch Fyne, while with respect to its easy communication 
with the sea the most similar subdivision of the Area is the Central Arran Basin. 

Observations were usually made between Toward and Bogany on the Bute Plateau, 
frequently in Rothesay Bay, at the topographical mouth of Loch Strivan in mid-channel 
off Strone Point, at Clapochlar in the deepest water rather more than half way up the 
loch, and in shallow water close to the head of the loch. The weather was more frequently 
stormy or wet whilst this division was being examined than in the case of any of the 
others, its free opening to the south allowing the swell coming up the Channel between 
Bute and the mainland to run straight up the loch. 

The curves of vertical distribution of temperature need not be considered here in 
detail. They conformed, as a rule, to the types of the Arran Basin, rarely showing an 
approach to those of Loch Goil. On several occasions these curves showed high hetero- 
thermicity, layers of water at different temperatures being sharply superimposed almost 
without mixture. 

I propose here to deal with the change of temperature of the loch as a whole as 
deduced from the temperature sections constructed for each trip. An exception may, 
however, be made with regard to the time-depth diagram at Clapochlar (fig. 5, Plate VI.). 
1 1 corresponds in depth with Stuckbeg, and shows a restricted circulation in the lower 



CLYDE SEA AREA. 137 

layers comparable with that of Loch Goil, though much less marked. In 1886, the 
diagram shows that the surface water was above 50° from July 10th to October 18th, or 
three weeks shorter than at Stuckbeg, but the temperature of 50° reached the bottom by 
October 15th, and the water there remained warmer than 50° until December 5th, 
whereas in Loch Goil the maximum depth to which this isotherm reached was 1 8 fathoms 
on November 12th. In 1887, the surface was over 50° from June 12th until November 
12th, and the bottom was at or above this temperature from November 20th until 
December 5th, whereas in Loch Goil the greatest depth reached by the isotherm was 
20 fathoms on November 28th. The persistent low temperature of the lower layers in 
the summer of 1887 was remarkable. In 1888, the surface was above 50° from July 7th 
until after the end of October, but on this occasion the greatest depth reached by the 
isotherm was 25 fathoms on September 24th, contrasted with a depth of 11 fathoms on 
September 3rd in Loch Goil. The isotherms became vertical at the minima, showing the 
phenomenon of homothermic change for a considerable time before and after that 
period. 

Temperature Sections of Loch Strivan. — These sections (figs. I. to XXIIL, Plates 
XIX. and XX.) are twenty-three in number. 

I. lith April 1886. — A general seaward dip was noticeable in the upper isotherms, 
corresponding to a northerly breeze blowing almost directly down the loch ; but below 
the depth of 5 fathoms the water was practically homothermic. 

II. 17th-lSth June 1886. — The water was well stratified in temperature, all the 
isotherms showing a pronounced seaward dip. The isotherm of 45° was 1 fathom deep at 
the head, and 15 fathoms at Bogany, while that of 43° dipped from 4 fathoms at the 
head to 40 fathoms half-way down the loch. The wind, on both days varied from north- 
west, light, to N.N.W., fresh, blowing straight down the loch, and obviously driving the 
warm surface water seaward while the deeper layers welled up at the head. This fact was 
proved absolutely by density observations, showing that the surface water at the head of 
the loch was as salt as the bottom water in the deepest place, while the surface water at 
Bogany was very much fresher. On this occasion the surface water at the head of Loch 
Strivan was Salter than that at any other observed position in the Clyde Sea Area. The 
tide in Loch Strivan on this occasion was about half-flood, so that it tended to reduce the 
effect of wind circulation. 

III. 7 th August 1886. — The temperature throughout had increased rapidly since June, 
but the slope of the isotherms was still seaward in the main. In the upper part of the 
loch the isotherms were close and horizontal, indicating rapid surface-heating, probably 
due to the warmth of the air. The wind varied from N.N.W. to west, and was light ; 
on the previous day it had been southerly. 

IV. 25th September 1886. — A very marked rise of temperature had taken place 
mamly, it would appear, by the entrance of warm and nearly homothermic water from 
the Dunoon or Arran Basin. The ill-defined barrier at Bogany now served to separate 
water with temperatures from 50° to 48° from the warmer water at 51° to 53° outside. 

VOL. XXXVIII. PART I. (NO. 1.) S 



138 DR HUGH ROBERT MILL ON THE 

The isotherms were practically horizontal, and the wind was light from the south and 
south-west. 

V. 13^ November 1886. — Autumnal conditions had by this time fully set in, and the 
barrier had no effect of separating water at different temperature. Below 5 fathoms the 
water was homothermic about 51°'5, above that it grew cooler to the surface, the 
isotherms showing no perceptible dip. The wind was northerly and very light. 

VI. 23rd December 1886. — Rapid cooling had taken place throughout the whole 
mass of water, and the few isotherms which appeared on the section showed a slight 
seaward dip in the deeper layers, but were practically horizontal near the surface, thus 
showing no sign of any disturbance of equilibrium. The wind was variable, but very 
light. 

VII. 7 th February 1887. — Although the range of temperature in this section was 
small, the run of the isotherms was somewhat peculiar, probably representing the result 
of some considerable previous disturbance. A wedge of warm water (over 45°) ran at 
the depth of 1 5 fathoms from the head of the loch to beyond Clapochlar, with cooler water 
above and below. The upper 10 fathoms at Clapochlar were homothermic at 42°, but at 
the head and in the Dunoon Basin, on the other side, the surface-temperature was below 
40°. The wind was blowing pretty strongly from south-east and south, or straight up 
the loch, but the dip of the isotherms was too slight and indefinite to show the direction 
of circulation. 

VIII. 20th March 1887. — In this section the conditions were almost homothermic: 
the one isotherm, of 44°, which appeared showed a marked seaward dip at the head of the 
loch, but the total range between surface and bottom being only 0° # 4, no argument can 
be based upon it. The wind was very light from the west and south-west. 

IX. 6th May 1887. — Surface warming had fairly set in, and the isotherms showed 
a slight seaward dip as far as Bogany. The wind was light from the north-west and 
north, thus affording a sufficient explanation for the temperature diminishing from the 
mouth to the head of the loch. 

X. lith June 1887. — A typical section of summer heating is here presented. The 
isotherms, although varying in their inclination, showed on the whole a slight seaward 
dip. There was no wind at the time of observation. The patch of water below 46° over 
the plateau at the mouth of the loch appears as a striking feature in the section, but is 
in realit} 7 inconsiderable, as the temperature falls only a fraction of a degree lower. 

XL ISth-lUh August 1887. — This section resembles those for the previous August 
and September by illustrating the function of the plateau in barring off the cooler water 
inside from the warmer mass entering from the Arran and Dunoon Basins. There was a 
strong seaward dip of the isotherms from the head to Clapochlar, a horizontal run 
thence to Bogany, beyond which the lines spread out. This was well defined by the 
Sprung schicht between the temperatures 51° and 54°, and by the cooling of the surface 
water (contrary to the usual order in summer) from 56°'2 at Clapochlar to 54° - 8 at the 
Head. A fresh breeze blowing from the north-east accounted for this state of matters. 



CLYDE SEA AREA. 139 

XII. 28th September 1887. — In this section autumnal conditions are well shown. 
The warmest water, homothermic at 5 4° '5, was in the Arran and Dunoon Basins, but 
gradually gave place to heterothermic conditions on the Bute Plateau, where lower tem- 
peratures reigned on the bottom, and inside the loch basin lower still. In the loch the 
surface water had cooled down a little, so that there was an intermediate layer at a 
slightly higher temperature, but a slight tilt of the isotherms caused the upper cold layer 
to thin away toward the head of the loch where the warm zone came to the 
surface. A slight north-easterly breeze was blowing down-loch at the time. Below the 
level of the bar the isotherms were apparently horizontal. 

XIII. 2nd December 1887. — Four of the most interesting sections made during the 
whole course of the work on the Clyde Sea Area record the results obtained by Dr Murray 
in December 1887, and three of these he has described* in an article discussing the 
effect of wind on the circulation of water. They are included here in order to complete 
the set. On December 2nd the ordinary winter condition was established, a mass of 
warm water occupying Loch Strivan covered over and shut in seaward by colder water. 
The isotherms dipped strongly seaward, showing an up-draught of the warmer water at 
the head of the loch, and an in-draught of the colder bottom water from outside across 
the Bute Plateau. The wind was blowing a stiff breeze from W. by N., mainly trans- 
verse to the loch, but with a down -loch component which would become more powerfully 
felt at the junction with the Dunoon Basin, off Bogany. 

XIV. \Ath December 1887. — The change brought about in the twelve days elapsing 
since the last section was drawn was very remarkable. At the earlier date the surface- 
temperature was everywhere 48° or more, on the 14th it was 45° at the mouth of the 
loch, and diminished to 39°*3 at the head, where the water was muddy and quite fresh. 
The most interesting feature was a Sprung schicht in which the temperature rose from 
44° to 48° in a fathom and a half, at a mean depth of 6 fathoms. Beneath, the tempera- 
ture was almost homothermic at 49° ; above, almost homothermic at 43°. A gale 
from the south-west was blowing up the loch, banking up the cold fresh- water at the 
head, and causing the Sprung schicht, raising the warmer deep water to the surface at 
the mouth, where the isotherms of the Sprung schicht spread out like a fan. The dis- 
turbance due to wind at no point reached deeper than 10 fathoms. 

XV. lbth December 1887. — This section represents the distribution of temperature 
twenty hours later than No. XIV. ; in the meantime, the wind had fallen calm, and changed 
to a northerly direction. The air was cold, and ice formed on the nearly fresh water at 
the head of the loch. The up-loch dip of the isotherms had almost disappeared, except 
in the upper layer. The Sprungschicht had risen to 5 fathoms at the head, and as its 
component isotherms spread out down the loch, they assumed a marked seaward dip, 
indicating a reversal of the direction of vertical circulation. The homothermic layer in the 
deep part of the loch remained as before, but on the Bute Plateau the conditions had 
become heterothermic throughout. 

* Scottish Geographical Magazine, iv. (1888), p. 351. 



140 DR HUGH KOBEET MILL ON THE 

XVI. 19th December 1887. — A strong northerly wind was blowing down the loch, 
and all the isotherms showed, accordingly, a strong seaward dip. The water at the head 
of the loch was salt and clear, and was the warmest surface-water in the section, 48° 
compared with 43° "7 at the mouth. The run of the isotherms suggests that the deep 
water was being drawn up all along the section, and the reverse dip of the lower isotherms 
of 48° at the mouth, indicates the drawing in of colder water along the bottom. 

The three sections illustrate admirably the rapidity with which the entire vertical 
circulation of a long narrow basin may be reversed. 

XVII. 8th January 1888. — The water had by this time assumed a nearly homo- 
thermic condition, and had greatly cooled. The one prominent isotherm in this section, 
however, dipped strongly seaward. The wind was variable and squally, shifting from 
north-west and north-east to south. 

XVIII. 27 th January 1888.- — The wind was blowing a heavy gale from N.N.W. and 
north when the observations for this section were taken, and the solitary isotherm (45°"5) 
it bears, dipped seaward, as might be expected. The extreme range of temperature was 
from 45° '0 to 45°"8, and this approximation to homothermicity was undoubtedly largely 
due to the mixing effect of the strong wind. 

XIX. llth February 1888.— This is another almost homothermic section, showing, 
by a curious coincidence, a wedge-shaped inclusion of warmer water nearly in the same 
position as in February 1887 (see Section VIIL), and, like it, bounded by the isotherm 
of 45°. For the rest the water was simply homothermic, its extreme range, but for this 
inclusion, being from 44°*4 to 44 0, 8. The wind was northerly and light. 

XX. 2§th March 1888. — Here a minimal section presents an unusually complicated 
character, the central mass of the water being a little warmer than 43°, while above and 
seaward the water cools to 42 0, 1, and below it cools to 42°"8. The total range is so 
small that one cannot found any argument upon the run of the isotherms. There was a 
light north-east wind. 

XXI. 9th June 1888. — This is a mere fragment, showing the surface layers stratified 
by perfectly horizontal isotherms. The wind on this occasion was a light breeze from the 
west, and Dr Murray found that the surface water along the side of off-shore wind was 
about 48°, and on the side of on-shore wind about 51°. In the fraction of axial section 
the surface was at 49°*5. This shows how a transverse disturbance of the water may 
give no trace in a longitudinal section, even while very considerable mixing may be in 
progress. 

XXII. 20th September 1888. — Atypical "heating" section with isotherms on the 
whole horizontal is here given. Above 15 fathoms the isotherms were concave upward, 
and below that plane they dipped seaward, indicating possibly an inward current of nearly 
homothermic water over the Bute Plateau, and a slight upwelling at the head, which does 
not, however, extend quite to the surface. The wind was light from the north-east. 

XXIII. 20th October 1888. — This section shows a very close approach to homo- 
thermicity in the initial stage of cooling, the extreme range being from 50 o, 5 on the sur- 



CLYDE SEA AREA. 



141 



face to 49 0, 8 at the bottom. The state of matters is similar to that common at the same 
season in the Gareloch, but not shown in the deeper lochs. A light breeze was blowing, 
varyino- from east to south-east ; but, of course, the section affords no evidence of 
circulation. 

Taken as a whole these sections show that Loch Strivan is, from its physical and 
o-eooraphical peculiarities, the most subject of all the Clyde lochs to have its waters 
mixed and set in motion by the wind. 

Seasonal Variation of Temperature. — Fig. 49, Plate XXXII., shows the seasonal varia- 
tion of the temperature of the air at Rothesay, and of the water of Loch Strivan, considered 
for the superficial layer of 5 fathoms, the deepest layer between 30 and 40 fathoms, 
and the mass of the water taken as a whole, the temperatures being calculated from the 
sections. 

The relations between these curves differ entirely from those of Loch Goil or Loch 
Fyne, showing a resemblance rather to the curves of the more open Basins. The retarda- 
tion of the date of maximum temperature, after that of the air, was for the superficial 5 
fathoms 45 days, and for the bottom 10 fathoms 105 days, in 1886 ; the corresponding 
figures for 1887 were 39 and 119 ; an average for the two years of 42 days for the 
surface, and 112 days for the bottom layer. The average retardation of the maximum 
was 165 days in Loch Goil, and 123 days in Loch Fyne, at the depth of 30 to 40 fathoms, 
indicating the more rapid circulation of Loch Strivan. 

The periods of heating and cooling of the mass of water in Loch Strivan — calculated 
from the curve — may be compared with those of the other divisions given in Table XLV. 
The time is in days ; the rate, degrees per day. 



Table LV. — Period of Heating and Cooling, and Daily Bate of Change of 
Temperature, in Loch Strivan. 



Heating, 
1886. 


Rate 
per 
day. 


Cooling, 

1886-87. 


Rate 
per 
day. 


Heating, 

1887. 


Rate 
per 
day. 


Cooling, 
1887-88. 


Rate 
per 
day. 


Heating, 

1888. 


Rate 
per 
day. 


180 


0-060 


155 


0-059 


202 


0-049 


198 


0-052 


186 


0-050 



The minimum and maximum temperatures of the mass of water, so far as they can 
be deduced from the curves, are :— 41°"8, April 15th, 1886; 52°'4, September 26th, 
1886; 43°-3, March 1st, 1887; 53°% September 18th, 1887; 42° -9, April 4th, 1888; 
and 52 0, 2, September 27th, 1888. In duration and rate these figures correspond best 
with those of the Arran Basin. Considering the two periods which can be compared in 
all the divisions, we find the average number of days of heating and cooling respectively 
to be — 191 and 177, or in the ratio of 100 to 93. In this respect — the greater duration 
of heating than cooling — the affinity is with Loch Fyne, where the ratio was 100 : 91, 
rather than with the Arran Basin, where it was 100 : 100. 



142 



DR HUGH ROBERT MILL ON THE 



Table LVI. gives concisely the mean temperatures of the various layers of depth into 
which the sections were divided for convenience of calculation, and Table LVII. repre- 
sents similarly the rate of change of temperature between consecutive observations. The 
curves giving graphical expression to this table are not reproduced, as in the main they 
merely repeat the general features of other curves of rate of change. In both the tables 
only one of the temperature trips of December 1887 is included, in order to ensure some 
approximation to the same order of magnitude in the intervals considered. 



Table LVI. — Mean Temperatures at Various Depths in Loch Strivan. 







Days 
from Last. 




Mean Temperati 


ires. 




Section. 


Date. 


Mass 

Weighted 

Mean. 


0-10 fms. 


10-20 fms. 


20-30 fms. 


30-40 fms. 


I. 


14.4.86 




41-80 


42-23 


41-47 


41-40 


41-30 


II. 


17.6.86 


64 


44-90 


46-51 


43-81 


43-14 


43-07 


III. 


7.8.86 


51 


49-24 


50-83 


48-57 


47-34 


45-98 


IV. 


25.9.86 


49 


52 04 


53-45 


51-74 


50-07 


48-50 


V. 


13.11.86 


49 


50-46 


49-40 


51-20 


51-59 


51-55 


VI. 


23.12.86 


40 


46-57 


45-87 


46-93 


47-38 


47-97 


VII. 


7.2.87 


46 


43-45 


42-37 


44-73 


44-00 


44-00 


VIII. 


20.3.87 


41 


43-65 


43-45 


43-70 


43-89 


44-00 


IX. 


6.5.87 


47 


44-80 


45-33 


44-44 


44-26 


44-15 


X. 


14.6.87 


39 


48-19 


49-60 


47-59 


46-27 


46-05 


XL 


13.8.87 


60 


52-18 


55-01 


52-00 


49-66 


48-26 


XII. 


28.9.87 


46 


53-04 


53-83 


53-32 


51-69 


49-65 


XIII. 


2.12.87 


65 


49-25 


48-89 


49-38 


49-69 


50-10 


XVII. 


8.1.88 


37 


45-88 


45-64 


45-99 


46-19 


46-40 


XVIII. 


27.1.88 


19 


45-23 


45-18 


45-39 


45-56 


45-70 


XIX. 


11.2.88 


15 


44-67 


44-58 


44-74 


44-76 


44-75 


XX. 


27.3.88 


45 


42-84 


42-71 


43-04 


42-87 


42-85 


XXI. 


20.9.88 


177 


5207 


53-80 


51-39 


49-95 


48-55 


XXIII. 


20.10.88 


30 


50-34 


50-35 


51-13 


50-02 


49-90 



Table LVII. may be compared with Table LIIL, which gives the corresponding- 
data for Loch Goil. In both lochs the rate of change of temperature in the surface 
layers is the same, o, 0G2 per day, or equivalent to 1° in 16|days; but the average 
change of the whole mass is 0° - 053 per day, or 1° in 19 days, contrasted with 23 days 
for Loch Goil and 13^ for the Gareloch. From 30 to 40 fathoms the rate of change in 
Loch Strivan was more rapid than in the other deep lochs, being equivalent to 1° in 20| 
days as compared with 30 in the other cases. The peculiarity visible in Loch Goil 



CLYDE SEA AREA. 



143 



of a Gradual diminution in the rate of heating as the depth increased until, in the bottom 
layer of 10 fathoms, the rate was scarcely more than half that in the surface layer, was 
also shown in Loch Strivan ; and a corresponding increase in the rate of cooling as the 
depth increased (leaving out of account, in this case, the superficial 10 fathoms). In 



Table LVII. — Average Change of Temperature per diem in Loch Strivan. 



Trip. 


No. of Days. 
Interval. 


Mass. 


0-10 fms. 


10-20 fms. 


20-30 fms. 


30-40 fms. 


17.6.86 


64 


+ 0-048 


+ 0-051 


+ 0-037 


+ 0-027 


+ 0-028 


7.8.86 


51 


+ 0-085 


+ 0-085 


+ 0-093 


+ 0-082 


+ 0-057 


25.9.86 


49 


+ 0-057 


+ 0-053 


+ 0-065 


+ 0-056 


+ 0-051 


13.11.86 


49 


- 0-032 


-0-083 


-o-ooi 


+ 0-031 


+ 0-062 


23.12.86 


40 


-0-097 


- 0-088 


-0-107 


-0105 


- 0-089 


7.2.87 


46 


-0-068 


- 0-076 


- 0-048 


-0-073 


- 0-086 


20.3.87 


41 


+ 0-005 


+ 0-026 


- 0-024 


- 0-002 


- o-ooo 


6.5.87 


47 


+ 0-034 


+ 0-040 


+ 0-016 


+ 0-008 


+ 0-003 


14.6.87 


39 


+ 0-087 


+ 0-109 


+ 0-077 


+ 0-049 


+ 0-046 


13.8.87 


60 


+ 0-066 


+ 0-090 


+ 0-074 


+ 0-057 


+ 0-037 


28.9.87 


46 


+ 0-019 


- 0-026 


+ 0-029 


+ 0-044 


+ 0-030 


2.12.87 


65 


- 0-058 


- 0-076 


-0-060 


- 0-030 


+ 0-007 


8.1.88 


37 


-0-091 


- 0-088 


- 0-092 


-0-095 


- o-ioo 


27.1.88 


19 


-0-034 


- 0-024 


- 0-032 


-0033 


- 0-037 


11.2.88 


15 


- 0-037 


- 0-040 


-0-043 


-0-053 


-0-064 


27.3.88 


45 


- 0-040 


- 0-042 


- 0-038 


-0-042 


- 0-042 


Mean Hea 


ting . 


+ 0-050 


+ 0-065 


+ 0-056 


+ 0-044 


+ 0-035 


No. of Cas 


es 


8 


7 


7 


8 


9 


Mean Coo 


ling . 


- 0-057 


-0060 


- 0-049 


-0054 


-0-069 


No. of Cas 


es 


8 


9 


9 


8 


6 


Mean Cha 


age . 


0-053 


0062 


0-052 


0-049 


0-049 



the surface layer the rates of heating and cooling were nearly equal, that of heating 
being 8 per cent, greater, but the rate of heating diminished, and that of cooling 
increased so rapidly that, at the bottom, cooling was twice as rapid as heating ; the 
disparity being somewhat greater than in Loch Goil. The bottom curve, in fact (see fig. 
49, Plate XXXII. ), rose only half as rapidly as the surface curve, but fell at the same rate to 
a simultaneous minimum. The air curve cut both the surface and the mass temperature 



144 



DR HUGH ROBERT MILL ON THE 



curves practically at the maxima. The air was warmer than the superficial 5 fathoms of 
water for 1G4 days in 1886, 126 in 1887, and 134 in 1888, an average of 141 ; and the 
air was colder than the superficial layer for 220 days in 1886-87, and 230 in 1887-88, 
an average for the two seasons of 225 days. The average of the two complete cycles is 
145 days of air warmer than water, and 225 of water warmer than air, or rather more 
than 4£ months of the former to rather less than 7\ months of the latter. The propor- 
tions being very similar to those for the other divisions. 

By interpolating probable values for the earlier months of 1886 and the later of 1888, 
we are able to present in Table LVIII. the approximate annual mean temperatures of 
water and air in Loch Strivan. 



Table LVIII. — Mean Annual Temperature of Air and Water for Loch Strivan. 



Year. 


I. Air. 
Mean for Area. 


II. Air. 
Mean for 
Rothesay. 


III. Water. 
0-5 fathoms. 


IV. Water. 

Mass. 


Difference. 
Air II. and 
Water III. 


Difference. 
Air II. and 
Water IV. 


18S6 . . 

1887 . . 

1888 . . 
Mean . 


46-2 

47-0 
46-7 


46-4 
47-4 
46-9 


47-0 
48-6 
48-2 


46-4 

48-1 
47-3 


-o-6 

- I"2 

-i'3 


o-o 
-0-7 
-0-4 


46-63 


46-90 


47-91 


47-27 


- I'OI 


-°"37 



As regards the excess of the temperature of the mass of the water in Loch Strivan 
over that of the air, the result is the same as for Loch Fyne and Loch Goil ; but the 
excess of surface-temperature is less than in any other division. For the average of the 
two years, 1886 and 1887, the surface water was warmer than the local air-temperature to 
the following amount : — In the Channel, l° - 7 ; Arran Basin, 1°*7 ; Loch Fyne, 1° # 5 ; 
Gareloch, 1°*8 ; Loch Goil, 1°*8 ; and Loch Strivan only 0°*9. This fact is evidently 
connected with the ease with which the water of Loch Strivan is mixed by wind through- 
out its whole depth ; thereby the mass of its water is brought more fully in contact with 
the air than in any other division. 

The average temperature of the surface water for the three years under observation 
was the same for the Gareloch, Loch Goil, and Loch Strivan, this being about half a 
degree higher than for Loch Fyne. 



The Dunoon Basin. 

The Dunoon Basin is here considered as the channel extending from the end of the 
north-eastern brancL of the Arran Basin, past Dunoon and up " Lower Loch Long," 



CLYDE SEA AREA. 145 

terminating at the bar which separates Loch Goil, and at the entrance to Upper Loch 
Long, just beyond the depression at Dog Roek. 

The set of observations in this division was usually an interrupted one, and rarely, if 
ever, were all the stations studied on the same day. Consequently, the sections which 
were drawn are somewhat less trustworthy than those for the lochs, and it has not been 
considered necessary to reproduce them. They were, however, quite serviceable for 
calculating the average temperature of the water on the occasion of each trip, and this 
was done in order to compare the temperature changes as a whole with those of the other 
divisions. Table LIX. gives the calculated temperature of the layers and of the- mass 
of water as a whole ; and Table LX. shows the rate of change of temperature between 
the dates of successive sections. The curves at the various stations did not differ much 
from those for water of the same depth in the Arran Basin, except in the case of the 
Dog Eock observations, which showed some affinity to those in the deep lochs. (See 
Loch Goil, p. 122.) 

The time-depth diagrams for the station off the Gantock Beacon opposite Dunoon, 
and for the Dog Bock soundings reproduced in figs. 10 and 11, Plate VI., show a general 
homothermic change in the deeper layers with a slightly greater restriction at Dog Rock. 
At the latter station contorted curves, showing layers of water varying irregularly in 
temperature, were very frequently found, due probably to the outflow from Loch Goil 
and Loch Long entering at different levels the mass of water in the Dunoon Basin. 

These diagrams show that in 1886 the temperature on the surface was above 50° from 
June 28th to October 28th at Gantock, and from May 10th to October 25th at Dog 
Rock, as compared with July 10th to November 6th in Loch Goil, where the greatest 
depth reached by that temperature was 18 fathoms. In contrast, the bottom water at 
Gantock was over 50° from August 27th to October 30th, and at Dog Rock from 
August 30th to December 8th. The observations for 1887 and 1888 showed exactly the 
same arrangement, with some slight differences of date. 

At Gantock the retardation of the date of maximum bottom temperature after 
the surface averaged 27 days, at Dog Rock 40 days, and in Loch Goil, at Stuckbeg, 116 
clays. The retardation of the minimum temperature at the bottom was 16 days after 
that at the surface at Gantock, 37 at Dog Rock, and 38 at Stuckbeg. The contrast is 
greatest between Dog Rock and Stuckbeg, the retardation of both maximum and mini- 
mum being practically equal at the former, while at the latter the descent of low tem- 
perature took place at the same rate, but the descent of the high temperature wave 
took three times as long. The date of surface maximum and of surface minimum 
corresponded closely for all three stations. The average number of days during which 
heating and cooling continued for the two complete periods was in the order — Stuckbeg, 
Dog Rock, Gantock— 186: 165, 169:168, 182:157 for the surface, and 255:105, 
172 : 180, 189 : 171 for the bottom. Thus, at Stuckbeg, the water was 21 days 
longer in heating than in cooling at the surface, and 150 days longer in heating than in 
cooling at the bottom. At Dog Rock the time was the same, both for heating and 

VOL. XXXVIII. PART I. (NO. 1.) T 



146 



DR HUGH ROBERT MILL ON THE 



cooling at the surface, but at the bottom the period of heating was 8 days shorter 
than that of cooling. At Gantock, on the other hand, the surface water required 
25 days, and the bottom water 18 days longer to heat than to cool. 

The contrast in this particular is the remarkable lengthening of the period of heating 
and diminution of the period of cooling at the bottom in the enclosed loch ; or, since the 
time required for a given change of temperature is the reciprocal of the rate of change, 
the average rate of heating is smaller and that of cooling much greater in an enclosed than 
in a relatively open basin. This is evidently due to restriction of circulation in the 
water. 



Table LIX.— M ean Temperature at Various Depths in Dunoon Basin. 













Mean Temperatures. 






Section. 


Date. 


Interval. 
Days. 
















Mass 
(Wtd.). 


5 fms. 


15 fms. 


25 fms. 


35 fms. 


45 fms. 


55 fms. 


I. 


17.4.86 




42-12 


42-70 


41-85 


41-70 


41-50 


41-45 


41-40 


II. 


19.6.86 


62 


45-78 


47-75 


44-82 


44-17 


44-00 


43-94 


44-23 


III. 


6.8.86 


48 


49-33 


50-86 


48-64 


48-05 


47-89 


47-83 


47-40 


IV. 


26.9.86 


51 


52-74 


52-97 


52-80 


52-46 


52-27 


51-89 


51-85 


V. 


12.11.86 


47 


50-95 


50-43 


51-20 


51-36 


51-47 


51-54 


51-36 


VI. 


24.12.86 


42 


46-34 


45-62 


46-52 


46-99 


47-38 


47-46 


47-24 


VII. 


6.2.87 


44 


43-75 


43-00 


44-13 


44-32 


44-48 


44-50 


44-50 


VIII. 


24.3.87 


52 


43-28 


43-18 


43-26 


43-41 


43-50 


43-53 


43-60 


IX. 


7.5.87 


45 


44-86 


45-73 


44-42 


44-19 


44-10 


44-16 


44-27 


X. 


14.6.87 


38 


48-88 


51-00 


48-34 


46-79 


46-28 


46-13 


46-30 


XI. 


7.8.87 


44 


54-01 


55-80 


53-86 


52-09 


51-15 


50-82 


50-83 


XII. 


30.9.87 


54 


54-01 


54-19 


54-03 


54-01 


53-94 


53-85 


53-79 


XIII. 


30.11.87 


61 


48-26 


48-00 


48-50 


48-40 


48-35 


48-35 


48-30 


XIV. 


11.2.88 


73 


44-34 


44-28 


44-28 


44-47 


44-51 


44-55 


44-39 


XV. 


8.3.88 


25 


44-01 


44-30 


43-71 


43-88 


44-05 


44-12 


44-25 


XVI. 


28.3.88 


20 


42-29 


42-05 


42-43 


42-48 


42-46 


42-36 


42-38 



Fig. 50, Plate XXXII., gives the seasonal change of temperature of the air over the 
Dunoon Basin taking this as the mean of the air at Greenock and Eothesay, of the 
superficial 5-fathom layer of water, and of the layer between 30 and 40 fathoms, as well 
as of the mass of water. The period represented comprises two maxima and three 
minima. In their general form the curves resemble those of the Arran Basic and 
Loch Strivan, showing the characteristic lag of the deeper layers in heating, and the 
much less obvious lag of the deeper layers in cooling. 

The retardation of the period of maximum in the surface water (5-fathom layer) 



CLYDE SEA AREA. 



147 



after the maximum of the air-temperature was 49 days in 1886, and 36 in 1887 ; while 
for the bottom layer of ten fathoms it was 70 in 1886, and 80 days in 1887 ; an average 
of 42 for surface and 75 for bottom retardation. The retardation for the deep water was 
less than half as great as for the same depth in Loch Goil, 60 per cent, shorter than for 



Table LX. — Average Change of Temperature per diem in Dunoon Basin. 



Date. 


No. of 

Days. 

Interval. 


Mass 

of 
Water. 


0-10 fnis. 


10-20 fms. 


20-30 fms. 


30-40 fms. 


40-50 fms. 


Over 
50 fms. 


19.6.86 


62 


+ 0-059 


+ 0-081 


+ 0-048 


+ 0040 


+ 0-040 


+ 0-040 


+ 0-045 


6.8.86 


48 


+ 0-074 


+ 0-065 


+ 0-080 


+ 0-081 


+ 0-081 


+ 0-081 


+ 0-066 


26.9.86 


51 


+ 0-067 


+ 0-041 


+ 0-081 


+ 0-086 


+ 0-086 


+ 0-080 


+ 0-086 


12.11.86 


47 


- 0-038 


- 0-054 


-0-034 


-0-023 


-0-017 


- 0-008 


-0-010 


24.12.86 


42 


-0-110 


-0-115 


-0111 


-0-104 


- 0-097 


- 0-097 


-0-098 


6.2.87 


44 


-0-059 


-0-059 


-0054 


-0-060 


-0-066 


- 0-067 


-0062 


24.3.87 


52 


-0-009 


+ 0-003 


-0-016 


-0-017 


-0-019 


-0-019 


-0-017 


7.5.87 


45 


+ 0-035 


+ 0-057 


+ 0-025 


+ 0-017 


-0-013 


-0-014 


-0-015 


14.6.87 


38 


+ 0-105 


+ 0-139 


+ 0-103 


+ 0-069 


+ 0-057 


+ 0-052 


+ 0-053 


7.8.87 


44 


+ 0-116 


+ 0-109 


+ 0-125 


+ 0-120 


+ 0-110 


+ 0-106 


+ 0-103 


30.9.87 


54 


0-000 


- 0-030 


+ 0-003 


+ 0-035 


+ 0-052 


+ 0-056 


+ 0-055 


30.11.87 


61 


-0-094 


-o-ioo 


-0-090 


-0-091 


-0-091 


-0-090 


-0-090 


11.2.88 


73 


- 0-053 


-0-051 


- 0059 


- 0-053 


-0-052 


-0-052 


- 0-053 


8.3.88 


25 


-0-013 


+ 0-001 


-0-023 


- 0-023 


-0019 


-0-017 


- 0-007 


28.3.88 


20 


-0-086 


-0-112 


-0064 


- 0-070 


-0-079 


- 0-088 


-0-093 


Average ) 
Heating J 


... 


+ 0-074 


+ 0-062 


+ 0-066 


+ 0-064 


+ 0-071 


+ 0-069 


+ 0-068 


Times 




6 


8 


7 


7 


6 


6 


6 


Average ) 
Cooling j 




- 0-058 


-0-074 


- 0-056 


-0-055 


-0-050 


-0-050 


-0-049 


Times 




8 


7 


8 


8 


9 


9 


9 


Average ) 
Change J 




0-065 


0-068 


0061 


0-059 


0-058 


0058 


0-051 



Loch Fyne, and 40 per cent, shorter than for Loch Strivan ; the obvious explanation 
being the much greater freedom of circulation in the Dunoon Basin than in the enclosed 
lochs. In other words, change of temperature throughout the mass is carried on more by 
mixture than by conduction. 



148 



DE HUGH EOBEET MILL ON THE 



The dates of the minimum and maximum temperature of the whole mass of water, 
and the temperatures at those epochs, as deduced from the curves, were as follows : — April 
15th, 1886, 42 o, 0; September 22nd, 1886, 52 0, 6 ; March 15th, 1887, 43°*4 ; September 
1st, 1887, 55 o, 0; and April 15th, 1888 y 42°*0. The duration of. warming in days, and 
the average rate of gain of temperature in degrees per day in the mass of the water, were 
as in Table LXI. 



Table LXI. — Period of Heating and Cooling and Daily Rate of Change of Temperature in 

Dunoon Basin. 



Heating, 
1886. 


Eate 
per day. 


Cooling, 
1886-87. 


Eate 
per day. 


Heating, 
1887. ' 


Eate 
per day. 


Cooling, 

1887-88. 


Eate 
per day. 


160 


+ 0°-066 


174 


-0°-053 


170 


+ 0°-070 


227 


-0°-57 



This approaches the distribution in the Arran Basin and Loch Strivan. The 
average number of days of heating was 165, and of cooling 200; the ratio of the 
time of heating to time of cooling being 100 : 121. The Channel and the Gareloch 
are the only other divisions in which the time of cooling approached the same high 
figure ; in the Arran Basin the periods of heating and cooling were the same, and in 
the loch basins heating was the process requiring more time. As shown in Table LX. 
the average rate of heating was 0°'074 per day, and the average rate of cooling 0°'058 ; 
in other words, it required on the average 1 3|- days to raise the temperature of the mass 
of water 1°, and 17 days to lower it by the same amount. The rate of change of 
temperature decreased very slightly with increasing; depth. 

The air was warmer than the surface layer of 5 fathoms for 165 days in 1886, and 
for 120 in 1887, or an average of 143, while it was colder for 210 days in 1886-87, and 



Table LXII. — Mean Annual Temperature of Air and Water for the Dunoon Basin. 



Year. 


I. Air. Mean 
for Area. 


II. Air. Mean 

for Eothesay 

and Greenock. 


III. Water. 
0-5 fms. 


IV. Water. 
Mass. 


Difference. 
Air II. and 
Water III. 


Difference. 
Air II. and 
Water IV. 


1886 .... 

1887 .... 


46-2 
470 


46-0 

47-2 


46-9 

48-8 


46-6 
48-5 


-0.9 
-i-6 


-o-6 
-i"3 


Mean . . . 


46-60 


46-60 


47-37 


47-07 


-i'»5 


-°'95 



CLYDE SEA AREA. 149 

for 225 days in 1887-88, averaging 217 for the two years, nearly the same as for the 
other divisions. 

By interpolating the values for the first three months of 1886, the mean annual 
temperatures of air and water may be compared as taken from the curve. The figures 
are given in Table LXII. 

Next to Loch Strivan (0°'9), no other division of the Area showed so low an excess 
of surface water-temperature over the air as 1° # 2. Gareloch and Loch Goil showed 
1 0, 8, Arran Basin and Channel 1°*7, and Loch Fyne 1°*5. The difference is, however, 
very trifling, and may well lie within the limits of probable error. The surface water 
was practically of the same temperature as that of Loch Strivan, but the mass of water 
was o, 3 warmer in the Dunoon Basin, or 0°'7 warmer than the mass of water in Loch 
Goil. 

General Summary. 

The scattered facts as to the thermal conditions of the Area are brought together 
in Tables LXIII. to LXVIL, in order to make the similarities and contrasts between 
the various divisions more marked. The only omissions are in the cases of the 
Great Plateau, the Estuary, Loch Long, Loch Ridun and the Kyles of Bute, and the 
Holy Loch. For the treatment of these there were either insufficient data, or no prospect 
of finding results materially different from those for the similar divisions which have 
been critically considered. All the figures in the tables are not equally trustworthy : the 
method by which they were obtained is fully explained, and their relative value indicated 
under the heads of the respective divisions. Table LXIII. gives an approximation to the 
monthly mean temperature of the superficial 5 fathoms of water, calculated from the 
seasonal curves of each of the seven divisions which are considered. The Gareloch was, 
speaking generally, the warmest from May to September, and the coldest from October 
to April. Its slight depth and land-locked character, and its exposure to the extreme 
changes of temperature in the Estuary, combine to make it the most responsive to 
changes in seasonal heating or cooling power. The Channel, in which oceanic influences 
predominate over solar, was usually the warmest division from October to March, when 
winter cooling was most active everywhere. During the summer months of 1887, the 
Channel was colder than any other division, but at the same season in 1886, and probably 
in 1888 also, the lowest surface temperatures were found either in Loch Fyne or 
Loch Goil. 

The month of minimum surface temperature was usually the same in all the 
divisions, and was April in 1886, March in 1887, and in 1888 both March and April. 
At this season the surface temperature was nearly the same over the whole Area, the 
greatest difference between the divisions being under 1°"5. The month of maximum in 
1886 was September for the Channel and Gareloch, and October for the other divisions. 
In 1887 it was August for the Gareloch, and September for the rest, and in 1888 it was 
September for all the places where observations were made. The period of greatest 



150 



DR HUGH ROBERT MILL ON THE 



Table LXIII. — Monthly Mean Temperature of Surface 5-Fathom Layer in the Divisions 

of the Clyde Sea Area, from Curves. 

1886. 



Division. 


Jan. 


Feb. 


Mar. 


April. 


May. 


June. 


July. 


Aug. 


Sept. 


Oct. 


Nov. 


Dec. 


Channel, . . 








42-lf 


44-6 


47-5 


50-1 


52-8 


55-0* 


52-1 


50-2* 


49-0* 


Arran Basin, . 








43-5* 


45-1 


47-2 


51-0 


53-2 


53-6 


51-9 


49-3 


46-6 


Dunoon Basin, 








42-4 


44-5 


47-7 


50-0 


51-6f 


53-2 


52-0 


49-5 


45-1 


Loch Strivan, . 








42-4 


44-4 


47-1 


50-0 


52-5 


54-0 


52-0 


49-0 


46-3 


Loch Fyne, . 








42-2 


44-2f 


46-8t 


50-0 


53-0 


53-0 


50-7f 


48-3f 


45-4 


Loch Goil, . . 








43-1 


44-7 


47-2 


49-8f 


51-6f 


52-2f 


51-6 


49-8 


46-6 


Gareloch, . . 
Mean, . . 








43 


45-6* 


48-7* 


52-0* 


53-5* 


53-8 


52-6* 


49-2 


44-61 








42-7 


44-7 


47-5 


50-4 


52-6 


53-5 


51-8 


49-3 


46-2 


Change of temp. 








+ 2 


•0+2 


•8+2 


•9+2 


•2+0 


•9 -1 


•7 -1 


•5-3 


•1-2-2 


Range between ^ 


























highest (*) and - 








1-4 


1-4 


1-9 


2-2 


1-9 


2-8 


1-9 


1-9 


4-4 


lowest (f), . ' 




































1887. 














Channel, 


47-2* 


44-6* 


44-1* 


44-8 


46 -Of 


48-4f 


51-6f 


55-3 


55-9* 


54-0* 


51-4* 


48-2* 


Arran Basin, . 


44-2 


42-9 


42-9 


45-2* 


48-0 


51-8 


54-4 


55-2 


55-2 


53-8 


50-8 


47-0 


Dunoon Basin, 


43-0 


42-5 


42-8 


44-4 


47-2 


51-6 


55-2 


56-8 


55-3 


52-4 


48-6 


46-0 


Loch Strivan, . 


43-6 


41-5f 


42-6 


44-6 


46-8 


50-4 


53-5 


55-8 


54-8 


52-2 


50-0 


47-2 


Loch Fyne, 


44-0 


43-7 


43-9 


45-2* 


47-8 


50-8 


53-2 


54-41 


54-Of 


52-4 


49-0 


45-3 


Loch Goil, . 


43-6 


42-1 


42-7 


45-1 


48-1* 


51-0 


55-0 


57-5 


55-6 


51-8 


48-2 


46-3 


Gareloch, . . 
Mean, . . 


42-8f 


42-3 


42-4f 


44-2f 


47-3 


52-0* 


56-8* 


58-0* 


55-6 


51-5f 


47-21 


44-8f 


44-0 


42-8 


43-0 


44-8 


47-3 


50-9 


54-2 


56-1 


55-2 


52-6 


49-3 


46-4 


Change of temp. 


-1 


•2+0 


•2 +1 


•8+2 


•5 +3 


•6+3 


•3 +1 


•9-0 


■9-2 


•6-3 


•3-2 


•9-1-4 


Range between \ 


























highest(*)and i- 


4-4 


3-1 


1-7 


1-0 


2-1 


3-6 


5-2 


3-6 


1-9 


2-5 


4-2 


3-4 


lowest (t), . ' 




































1888. 














Channel, . . 


46-4* 


44-3 


43-2 


42-9 


43-8 
















Arran Basin, . 


44-1 


42-9t 


42-4 


42-8 


















Dunoon Basin, 


45 6 


44-5* 


43-6* 


43-3 


















Loch Strivan, . 


45-2 


44-1 


42-8 


43-6 


46-0 


48-8 


51-8 


54-4 


54-9 


52-0 






Loch Fyne, 


44-4 


44-0 


43-1 


433 


45-0 


47-6 


50-0 


52-2 


53-2 








Loch Goil, . 


45-5 


44-3 


42-9 


44-5* 


47-1 


49-5 


52-0 


54-0 


54-7 


53-1 






Gareloch, . . 
Mean, . . 


43-9f 


43-3 


42-0t 


42-2f 


44-8 


48-8 


52-4 


55-2 


55-0 








45-0 


43-8 


42-9 


43-2 


















Change of temp. 


-1 


•2-0 


•9+0 


•3 




... 














Range between \ 


























highest (*) and [ 
lowest (f), . ) 


25 


i-6 


16 


2-3 











































CLYDE SEA AREA. 151 

difference between the surface temperature of different divisions was at or immediately 
before the maximum. Thus, in September 1886 the surface water in the Channel was 
6°*2 warmer than in Loch Goil, and in August 1887 that in the Gareloch was 7° '6 
warmer than in Loch Fyne. Comparing the years under observation, we find that in 
1887 the monthly temperature corresponded during the warming period with that two 
months later in 1886, and the maximum was on the average 2° higher. This was 
brought about by the spring minimum of 1887 being 1°'6 higher than in 1886 (0°*7 
higher than in 1888), and by the increment of temperature between April and May being 
1° greater, the succeeding monthly increments being a trifle less. The fall of temperature 
in 1887, between September and October, was l 0- 4 greater than in 1886, so that the 
averages for the succeeding six months in both years were nearly the same. 

The great feature of 1887, as regards surface temperature, was the rapid heating of 
early summer, leading to a higher surface maximum by bringing it on while the air 
temperature was still high, so that when the air-temperature began to fall it very 
speedily stopped farther heating. I have already shown, by reference to the invariable 
character of the surface temperature curve being cut at its maximum by the air-tempera- 
ture curve, that the more rapid the rate of heating, the higher is the limiting temperature 
reached, while the slower the rate, even when much longer continued, the lower is the 
ultimate maximum. Hence, in the warmest years for surface water, the retardation of 
the surface after the air maximum is the least, and the greater the retardation the lower 
is the maximum. The whole may be put tersely in the words, that for all parts of the 
Clyde Sea Area the surface water continues to heat until its temperature reaches that of 
the air ; as soon as this occurs surface-cooling sets in. 

Table LXI V. gives the monthly mean temperature of the mass of water in each division 
calculated from the curves. This is not such a readily comparable datum as the surface 
temperature, because of the difference in the average depth of the various basins and in 
their degree of isolation. In its figures we may, however, look for satisfactory evidence 
as to the influence of configuration on temperature. The minimum mass temperature 
occurred in April 1886, in March 1887, and in March or April 1888, thus coinciding in 
time with the minimum of the surface layers. The warmest month for the mass of water 
was September in the Channel and the Gareloch, October for all the other divisions in 
1886 ; August in the Gareloch and September in all the other divisions for 1887, this again 
corresponding to the date of surface maximum. The correspondence with surface 
changes is similarly shown by the fact that the Gareloch is the warmest division in 
summer and the coldest in winter; while the Channel is the warmest in winter, and Loch 
Fyne or Loch Goil usually the coldest in summer. From January to April 1888 Loch 
Fyne and Loch Goil were the warmest, their temperature being 1° higher than the 
Channel in February. While the greatest range between the warmest and coldest 
division as regards surface temperature was 5°"2, and the least 1°'0 ; the greatest range 
in mass temperatures was as much as 7°"6, and the least only o, 5. At, or immediately 
after, the minimum the mass of water in the various divisions was most nearly uniform 



152 



DR HUGH ROBERT MILL ON THE 



Table LXIV. — Monthly Mean Temperatures of the Mass of Water in the Divisions of the 

Clyde Sea Area, from Curves. 



_ 

18S6. 


Division. 


Jan. 


Feb. 


Mar. 


April. 


May. 


June. 


July. 


Aug. 


Sept. 


Oct. 


Nov. 


Dec. 


Channel, . . 








42-1 


44-6* 


47-5 


50-1 


52-8 


55-0* 


52-1 


50-2 


49-0* 


Arran Basin, 








42-3* 


43-5 


45-3 


47-7 


49-9 


51-3 


51-4 


49-7 


46-7 


Dunoon Basin, . 








42-2 


43-0 


45-4 


48-1 


50-0 


52-2 


52-4 


50-5* 


45-8 


Loch Strivan, . 








42-0 


42-8| 


44-8 


47-6 


50-0 


51-9 


52-4 


50-2 


47-3 


Loch Fyne, 








42-0 


42-8-j- 


44-3f 


46 -0t 


48-4 


49-6 


49-6 


49-lf 


47-6 


Loch Goil, . 








41 -8f 


43-1 


44-4 


46 -Of 


47-6f 


48-8f 


49-5f 


49-2 


47-5 


Gareloch, . . 
Mean, . . 








41-9 


44-4 


48-3* 


51-6* 


53-5* 


54-0 


52-6* 


49-4 


45-2t 








42-0 


43-5 


45-7 


48-1 


50-3 


51-8 


51-4 


49-8 


47 


Change of temp. 








+ 1 


•5+2 


•2+2 


•4+2 


•2 +1 


•5-0 


•4 -1 


•6-2 


•8-1-9 


Range between -i 


























highest (*) and !- 








0-5 


1-8 


4-0 


5 '6 


5-9 


6-2 


3-1 


1-4 


3-8 


lowest (f), ,) 
































1887. 










Channel, . . 


47-2* 


44-6 


44-1* 


44-8* 


46-0 


48-4 


51*6 


55-3 


55-9 


54-0* 


51-4* 


48-2* 


Arran Basin, . 


44-5 


43-7 


43-5 


44-4 


46-2 


48-4 


50-2 


52-0 


52-1 


50-41 


48-5 


46-3 


Dunoon Basin, . 


44-4 


43-5 


43-4 


43-7f 


45-6 


49-0 


52-6 


54-6 


54-8 


52-9 


50-0 


47-5 


Loch Strivan, . 


44-7 


43-4 


43-4 


44-2 


45-4 


48-5 


50-8 


52-4 


53-2 


52-6 


51-0 


47-8 


Loch Fyne, . 


45-6 


44-5 


43-8 


44-4 


45-6 


47-6 


49-2f 


50-4f 


51-2f 


50-8 


49-6 


47-6 


Loch Goil, . . 


46-0 


44-8* 


43-9 


44-2 


45-2f 


47 -3f 


50-0 


52-7 


52-8 


51-1 


49-4 


47-9 


Gareloch, . . 
Mean, . . 


43-2f 


42-6f 


42-8t 


44-1 


46-8* 


51-2* 


56-0* 


58-0* 


56-0* 


51-2 


47-4f 


45-5f 


45-1 


43-9 


43-6 


44-3 


46-8 


48-6 


51-5 


53-6 


53-7 


51-9 


49 6 


47-2 


Change of temp. 


-1 


■2-0 


•3+0 


■7+2 


•5 +1 


•8+2 


•9+2 


•1 +0 


•1 -1 


•8-2 


•3-2 


■4-1-6 


Range between 'i 
highest (*) and J- 
lowest (f), . ) 


























4-0 


2-2 


1-3 


11 


1-6 


3-9 


6-8 


7-6 


4-8 


3-6 


4-0 


2-7 






























1888. 










Channel, . . 


46-4 


44-3 


43-2 


42-9 


43-8 
















Arran Basin, . 


44-8 


43-4f 


42-3 


42-8 


















Dunoon Basin, . 


45-4 


44-4 


43-5 


42-2 


















Loch Strivan, . 


45-6 


44-4 


43-0 


43-1 


44-2 


46-4 


48-8 


50-9 


52-1 


51-6 






Loch Fyne, . 


46-0 


45-4* 


43-6* 


43-6* 


44-2 


46-0 


47-2 


48-2 


48-7 








Loch Goil, . 


46-7* 


45-4* 


43-6* 


43-0* 


44-5 


45-9 


47-5 


49-2 


50-9 


50-5 






Gareloch, . . 
Mean, . . 


44-lf 


43-6 


42-2f 


42-lf 


44 


48-0 


51-6 


54-2 


54-8 








45-6 


44-4 


43-1 


42-9 


















Change of temp. 


-1 


•2 -1 


•3 •- 


2 


















Range between \ 


























higheet(*)and > 
lowest (t), . i 


2-6 


2-0 


1-4 


1-5 











































CLYDE SEA AREA. 



153 



in temperature, the greatest diversity occurring at or before the maximum. Thus 
in July and August 1886 the Gareloch was 5° "6 and 5° "9 warmer than Loch Goil, and in 
September the Channel was 6° "2 warmer than Loch Goil. In July and August 1887 the 
Gareloch was 6° "8 and 7° "6 warmer than Loch Fyne, and about 6° warmer than the 
Arran Basin, the influence of depth and isolation showing itself to the full. 



Table LXV. — General Summary of Temperature Conditions in the Clyde Sea Area. 













Wa 


I'ER. 










AlK. 

Mean foi 


































1. Mean annual surface temperature, 1886 


Area. 


Channel. 


Arran 
Basin. 


Dunoon 
Basin. 


Loch 
Strivan. 


Loch 
Fyne. 


Loch 
Goil. 


Gareloch. 


Mean. 


46-2 


48-2 


47-4 


46-9 


47-0 


46-8 


47-1 


47-5 


47-3 


2. „ „ 1887 


47-0 


49-3 


49-3 


48-8 


48-6 


48-6 


48-9 


48-7 


48-9 


3. „ ,, 1888 


47-3 








48-2 


47-1 


47-9 


47-6 




4. ,, ,, 1886-87 


46-6 


487 


48-3 


47-8 


47'9 


477 


48-0 


48-1 


48-2 


5. Mean range, max. to min., 1886-87 


20 7 


123 


1 1 - 2 


12-5 


12-9 


io-8 


12-3 


133 


12*2 


6. Mean annual mass temperature, 1886 




48-2 


46-4 


46-6 


46-4 


45-8 


45 7 


47-4 




7. „ „ 1887 




49-3 


47-5 


48-5 


48-1 


47-5 


47-9 


48-7 




8. ,, ,, 1888 










47-3 


46-0 


47-1 


47-5 




9. „ ,, 1886-87 




487 


46-9 


47-1 


47'3 


46-6 


46-8 


48-1 


47 '3 


10. Mean range, max. to min., 1886-87 




12-3 


8-8 


io-8 


IO - I 


7'5 


8-3 


137 


IO-2 


11. Excess surface over local air, 1886 




1-7 


1-2 


0-9 


0-6 


1-3 


1-1 


1-0 


1-1 


12. „ „ 1887 




17 


2-3 


1-6 


1-2 


1-7 


2-5 


2-8 


2-0 


13. „ ,, 1888 










1-3 


0-5 


1-0 


0-3 




14. „ „ 1886-87 




17 


17 


1 "3 


0-9 


i-5 


i-8 


1-9 


1 "5 


15. Days air warmer than surface, 1886 




150 


147 


165 


164 


165 


172 


154 


160 


16. ,, ,, 1887 




105 


125 


120 


126 


120 


104 


94 


113 


17. ,, ,, 1888 










134 


150 


132 


155 




18. ,, ,, 1886-87 




134 


136 


143 


145 


143 


138 


124 


137 


19. Days air colder than surface, 1886 




244 


224 


210 


220 


216 


224 


245 


226 


20. „ ,, 1887 




230 


232 


225 


230 


222 


248 


250 


234 


21. ,, ,, 1886-87 




237 


228 


217 


225 


219 


236 


248 


230 


22. Eetarda. surf. max. after air, days, 1886 




48 


48 


49 


45 


45 


66 


54 


51 


23. „ „ 1887 




46 


46 


36 


39 


50 


42 


30 


41 


24. ,, ,, 1888 












35(?) 


20(?) 


20(?) 




25. ,, ,, 1886-87 




47 


47 


42 


42 


48 


54 


42 


46 


26. Retarda. 30-40 fms. max. after air. 1886 




48 


52(?) 


70 


105 


126 


180 






27. „ „ 1887 




46 


50(?) 


80 


119 


120 


150 






28. ,, „ 1886-87 




47 


5i(?) 


75 


112 


123 


165 




8 9 (<) 


29. Mean daily rate of mass-heating, 1886 


0-122 


0-090 


0-058 


0-066 


0-060 


0-047 


038 


0-081 




30. „ „ 1887 


0-125 


0-065 


0-046 


0-070 


0-049 


0-037 


0-058 


0-107 




31 - >■ ,, 1888 


0-125 








0-050 


0-033 


0-043 


0-079 




32. ,, ,, 1886-87 


0-124 


0-078 


0-052 


0-068 


0-054 


0-042 


0-048 


0-094 


0-062 


33. Mean daily rate of mass-cooling, 1886 


0-098 


0-065 


0-053 


0-053 


0-059 


0-039 


0-040 


0-070 




34 - „ „ 1887 


0-094 


0-062 


0-049 


0-057 


0-052 


0-045 


0-046 


0-064 




35. ,, ,, 1886-87 


0-096 


0-064 


0-051 


0-055 


0-056 


0-042 


0043 


0-067 


0-054 


36. Mean days cooling per 100 of heat, 1886 


106 


116 


92 


109 


86 


93 


73 


108 


97 


37. „ ' „ 1887 


145 


115 


107 


133 


98 


89 


131 


173 


121 


38. „ ,, 1886-87 


125 


115 


100 


121 


93 


9i 


99 


130 


109 



In Table LXV. the annual periods of temperature change are compared for the various 
divisions, the data being in each case taken from the curves and detailed tables which 
have already been fully discussed. The mean annual range, Nos. 5 and 10, is the 
difference between the monthly temperature for the coldest and warmest month of the year, 
as detailed in Tables LXIII. and LXIV. The values relating to surface conditions, and 
to those connecting surface and air, are averaged in the last column, as the air and surface 
layer of water being each continuous over all the divisions, may be looked on as parts of 

VOL. XXXVIII. PART I. (NO. 1). U 



154 DR HUGH ROBERT MILL ON THE 

one whole, and the averages may, accordingly, be accepted as approximately true for the 
Area as a whole. The mass temperatures for each year are not meaned, as the difference 
in the depth of the divisions deprives them of comparative value, and the same holds 
good for the retardation of temperature at great depths. The mean of the 1886-87 
average is given as a rough datum for comparison in all cases, even where it would 
require to be modified by weighting for difference in depth and volume in order to be 
truly comparable. 

Looking first at the general results for the two years 1886 and 1887, we find that 
the air-temperature in 1887 was 0°'8 higher than the previous year, while the temperature 
of the superficial 5 fathoms was 1°*3 higher ; and, taking account of the relation of surface 
temperature to local air-temperature for each division, the excess of surface water over 
air temperature was twice as great in 1887 as in 1886, i.e., 2° as compared with l°'l. 
The contrast between the two years was greatest in summer, and is best shown in the 
rapidity with which the surface temperature rose in 1887, the maximum being reached 
only 41 days after the air maximum, as compared with 51 days in 1886. Since it has 
been shown that the curve of surface water temperature rises until it is cut by the 
descending curve of air-temperature, rapid heating means a high surface maximum, and 
explains the somewhat curious fact that in 1887, the year of high water-temperature, the 
air was warmer than the water for 113 days only, as compared with 160 in 1886 ; and 
that in 1887 the period of mass-cooling of the water was 21 per cent, longer than that 
of heating, whereas in 1886 it was 3 per cent, shorter. Put briefly, the contrasted 
temperature results of the two years indicate that the longer the duration of heating 
in surface water the lower is the ultimate maximum, or that the rate of heating is 
proportional to the amount of heating. 

The range of temperature between the coolest and warmest months was, on the 
average of the two years, 20° '7 for the air, 12°*2 for the superficial 5 fathoms of water, 
and 10° "2 for the whole mass of water, thus indicating that sea-water in layers, averaging 
30 fathoms deep, is just half as responsive to temperature changes as the air at the 
Earth's surface ; while layers 5 fathoms deep, when resting on deeper water, are 60 per 
cent, as responsive as the surface air. The same result as to mass-heating is brought out 
by comparing the mean daily rate of seasonal heating and cooling, this being practically 
half as great in the water as in the air. 

Arranging the various divisions with reference to the difference of their data from 
those of the Channel, we are able to get a hint as to the modifying influence of depth 
and isolation. When this is done for the seven different elements of surface temperature, 
mass temperature, excess of surface over air temperature, surface retardation of maximum, 
retardation of maximum at 35 fathoms, rate of change of temperature in the mass, and 
proportion of time of cooling to that of heating, and the numeral expressing the position 
of the division in the series, the Channel being taken as zero, is written after its name : 
the sum of the numbers in each case would tend to approach equality if the order were 
merely accidental. If a well-defined order appears it cannot be accidental, but must 



CLYDE SEA AREA. 155 

point to some definite cause. Gareloch came first 5 times and second once, out of the 

six columns in which it appeared, its total being 7. This is interesting in showing how 

the thermal changes in a shallow, brackish, and nearly land-locked basin were almost the 

same in order and amount as those of the freely-exposed Channel, where the complete 

mixture of water by currents entirely neutralised the evidence of depth, and the free 

communication with the ocean seemed to make up for the reduced effect of radiation on 

a clear water surface remote from land. Arran Basin came first on 2 occasions, third on 

2 occasions, and fourth 3 times, the total being 20. Dunoon Basin, with a total of 21, 

may be taken as practically the same. It was never first, but was second on 4 occasions, 

third on 1, and fifth on 2. Loch Strivan had a total of 26, Loch Goil of 30, and Loch 

Fyne of 37. In the last case the position was fourth on 2 occasions, fifth on 1, and sixth 

4 times. The order of restricted, range, retarded phase, and lowered mean temperature is 

thus, following the Channel : — 

1. Gareloch. 
( Arran Basin. 
( Dunoon Basin. 

4. Loch Strivan. 

5. Loch Goil. 

6. Loch Fyne. 

Depth is obviously a factor of some importance, or Gareloch would, not come first, but it 
is a factor of very minor importance, or Arran Basin would not come second. The order 
of the larger basins and. deeper lochs is obviously that of the degree of isolation due to 
configuration of the basin, not alone to height of barrier, but to number of barriers, or 
Loch Goil would not come before Loch Fyne. 

The contrast between the Gareloch and Loch Fyne is very marked — comparing them, 
the former is found 0°'5 warmer on the surface, 1°"5 warmer in its mass, with a surface 
range between the extreme months 2 0, 5 greater, and a range in mass temperature 6 0, 2 
greater (almost double), with an average rate of change of seasonal temperature twice as 
great, and with its period of cooling, compared with that of heating, nearly 40 per cent, 
longer. 

Heat Transactions of the Clyde Sea Area. — So far the discussion has been limited 
to changes of temperature, because to compare the actual amounts of heat involved in 
the various transactions would be difficult without fuller evidence as to transverse 
sections, and as to the specific heat of sea-water of different salinity. A few preliminary 
calculations were made which may be placed on record, although they are but a rough 
approximation. According to Professor Thoulet of Nancy, * if the specific hea/t of pure 
water is taken, as unity, that of sea-water of density (As-se) 1 '00159 is 0*986 ; for density 
1-01162 it is 0-957, while for density 1*02666 it is 0'931. The formula for expressing 
the number of heat units in a mass of sea-water may be put as V x D x <r(t-t'), where V 
is the volume, D the density, o- the specific heat, and t-t' the change of temperature. 

* Thotjlet, Oceanographie — Statiquc, 1889, p. 298. 



156 



DR HUGH ROBERT MILT, ON THE 



But for the range of density which has to be considered, the value of Do- is practically a 
constant = 0"96 (range approximately from 0-959 to 0-961), and for the divisions under 
consideration, taking the volume of the Gareloch at half-tide as a convenient unit, we 
have the following values of VIV, where V is in every case the volume at half-tide, 
expressed in units of the capacity of the Gareloch.* 



Gareloch VDa- 


= 0-96 = 


1 


Loch Goil „ 


142 = 


1-48 


Loch Fyne „ 


= 18-52 = 


19-29 


Arran Basin „ 


= 663-77 = 


69143 



Table LXVI. gives the mean temperature of the mass of water in four divisions 
at the spring minima and autumn maxima, change of temperature, and the quantity 
of heat gained or lost, which is obtained by multiplying the change of temperature 
by the foregoing factors. The heat unit employed is the Gareloch-degree, or the 
amount of heat necessary to raise a mass of pure water equal to the half-tide contents of 
the Gareloch, from 32° to 33° F. Multiplying by 166,000,000 would give the value 
in ton-degrees, or multiplying by 371,840,000,000 would give it in Fahrenheit heat 
units. 



Table LXVI. — Total Heat Changes in the Water of the Clyde Sea Area. 



Division. 


Min. 
1886. 


Max. 
1886. 


Change. 


Heat 
gained. 


Min. 
1887. 


Change. 


Heat 
lost. 


Max. 

1887. 


Change. 


Heat 
gained. 


Min. 

1888. 


Change. 


1 
Heat 
lost. 


Gareloch . . 
Loch Goil 
Loch Fyne . 
Arran Basin , 


41°8 
41-8 
42-0 

42-0 


54-1 
49-8 
49-9 
51-6 


12°3 

8-0 
7-9 

9-6 


G. L. 

Units. 
12-30 

11-84 

IS2-39 

6637-73 


42-7 
43-7 
44-3 
43-6 


ll°-4 
6-1 
5-6 
8-0 


G. L. 

Units. 
11-40 

9-03 
108-02 

5531-44 


57-9 
56-1 
51-4 
52-2 


15-2 

12-4 

7-1 

8-6 


G. L. 

Units. 
15-20 

18-35 

136-96 

5946-30 


41-9 
43-3 
44-4 
42-5 


16°0 

12-8 

7-0 

9-7 


G. L. 

Units. 
1 6 -oo 

18-94 

135-03 
6606-87 



It thus appears that Loch Goil, on account of its greater volume, has about the same 
thermal power as the Gareloch, although its range of temperature is very much less. 
Loch Fyne has about ten times the thermal power, and the Arran Basin 500 times the 
thermal power of the Gareloch. Taking the average of heat gained and lost in the two 
years into account, along with the area of each of the divisions considered, we sec in 
Tabic LXVIL the actual thermal power per square mile, or the amount of heat stored or 
returned through each unit of area. 

Taking roughly 5 '5 Gareloch-degree units per square mile as the normal amount of 
heat exchange between successive maxima and minima, would give for the whole Area a 
total of 6403*8 units ; but estimating 6 units as a more probable value for the 
transference per square mile, we would get 6985, or nearly 7000 units. Table LXVII. 

* See Part I., Trans. Boy. Soc. Eilin. 



CLYDE SEA AREA. 



157 



shows how the amount of transference of heat per square mile depends on the depth of 
the water, each square mile of the Arran Basin receiving and parting with nearly three 
times as much heat as a square mile of the Gareloch, supposing all the heat to enter 
and leave by the surface. Earlier discussions showed, however, that a large part of the 
heat in the seaward division of the Area came not from the sun but from the sea, 
hence it is probable that distance from the Channel and isolation as well as the shallow- 

Table LXVII. — Heat Storing Power of the Divisions of the Clyde Sea Area. 



Division. 


Area. 


Gareloch-D egrees. 


Average 
Depth. 


Average 
Axial 
Depth. 


Average 

Heat Stored, 

1886-87. 


Average 
Heat Re- 
turned, 

1886-87. 


Heat Stored 

per square 

Mile. 


Heat Re- 
turned per 
sq. Mile. 


Gareloch, . . . 
Loch Goil, . . . 
LochFyne, . . . 
Arran Basin, . . 
Total, C. S. A., 


4-23 
336 

28-44 

685-00 

1164-33 


13-75 

15-09 

144-67 

6292-01 


13-70 

14-00 

121-52 

6019-15 


3-25 
4-49 
5-08 
9-18 


3-24 

4-16 
4-27 

8-78 


n 

14 

34 
29 


18 

m 

68 



ness of the water have a good deal to do with reducing the surface heat transactions. 
The difference in depth between Lochs Goil and Fyne would suggest a greater difference 
in thermal power than is found, while the difference in depth between Loch Fyne and 
the Arran Basin would suggest a less difference than occurs, if depth were the only or 
the main agent in producing the difference. We are probably not far wrong in sur- 
mising that from one-half to two-thirds of the heat stored and lost by the Arran Basin is 
independent of local solar radiation, and depends entirely on tidal mixture with sea-water. 

The total heat absorbed in a year and returned by the Clyde Sea Area must be 
equivalent to about 2,010,000,000,000,000,000 foot pounds. Taking a horse-power as 
33,000 foot pounds per minute, the heat of the Clyde Sea Area, as it is given out from 
September to March, is equivalent if it were all turned into work to the performance of 
an engine of 3,700,000 horse-power. 

It is interesting to notice that in 1887, notwithstanding the high maximum tempera- 
ture, much less heat was stored than in 1886, the low minimum with which 1886 started 
accounting for the fact. 



I do not profess to have exhausted my subject, for the observations would in several 
instances stand more rigorous treatment ; but there are so many points in which farther 



158 DR HUGH ROBERT MILL ON THE CLYDE SEA AREA. 

observations would be helpful or necessary that I think it best to postpone the more 
theoretical considerations until a time of greater leisure arrives, or a better-equipped 
physicist feels prompted to build on these foundations. My effort has been to suggest 
ways in which the data could be handled so as to draw from them only the general 
principles which they unmistakably suggest ; and I believe that I have employed no 
theory in this process which could vitiate the resulting conclusions. If, in the 
endeavour to avoid error, I have failed to arrive at the whole truth, doubtless others 
bolder and more skilful wil lfind it worth their while to work over the unexhausted slao;- 
heaps. May they be rewarded by much reducible ore ! 



( 159 ) 



CONTENTS AND SUMMARY OF PART III. -TEMPERATURE. 





PAGE 


Preliminary, .... 


1-3 


Instruments and Methods, 


3-13 


Surface Temperature, 


3 


Beep Sea Thermometer, . 


4 


Corrections, 


4 


The Scottish frame, 


5 


The " Medusa," and Equipments, 


6 


Table I. Mean Velocity of Fall o 


f 


Brass Weights in Sea- Water, 


7 


Table II. Time Occupied by Bras 


s 


Weights in Falling 10 Fathom 


s 


through Water, 


8 


Treatment of Temperature Results — 




Kecording Observations, 


8 


Plotting Curves of Vertical Distribu 




tion, 


9 


Seasonal Temperature Curves, 


9 


Temperature Sections, . 


9 


Calculation of Mass Temperature, 


10 


Time-Depth Temperature Diagrams, 


10 


Terminology Employed, 


11 


Types of Vertical Curves, 


11 


Table III. Mean Temperature of Ai 


r 


over Clyde Sea Area in 1886, 1887 


> 


1888, 


12 


Temperature Trips, 


13-31 


Table IV. Stations where Observations 




of Temperature were made, 


14 


Description of Temperature Trips — 




1. April 1886, 


15 


2. June „ 


16 


3. August „ 


17 


4. September „ 


18 


5. November „ 


19 


6. December „ 


20 


7. February 1887, 


20 


8. March-April „ 


21 


9. May 


22 


10. June „ 


23 


11. July 


24 


12. August „ 


25 


13. September „ 


26 


14. November-December „ 


27 


15. December 1887-January 1888, . 


27 


16. January „ 


27 


17. February „ 


28 


18. March 


28 



PAGE 

Description of Temperature Trips — contd. 

19. March 1888, . 29 

20. April „ . 29 

21. June „ . 30 

22. August-September „ . 30 

23. October „ . 31 

General Result of the Trips, . . 31 

Thermal Conditions op the Divisions op the 
Clyde Sea Area, .... 31-149 

The North Channel — 

Table V. Temperature Observations in 

the Channel, ... 32 

Homothermic Character of the Chan- 
nel, ..... 33 
Seasonal Change of Temperature in 

the Channel, ... 34 

Table VI. Rate of Change of Tempera- 
ture in the Channel, . . 36 

The Great Plateau — 
Table VII. Temperature Observations 
on the Plateau (Eastern 
Side), ... 38 

„ VIII. Rate of Change of Water- 
Temperature on the 
Plateau (Eastern Side), . 38 

„ IX. Temperature Observations 
on the Plateau (Western 
Side), ... 39 

General form of Temperature curve, . 39 

Hourly Observations on Plateau, . 41 

The Arran Basin — 
Table X. Temperature Observations 

off Carradale, . . 46 

„ XI. Temperature Observations 

off Loch Ranza, . . 47 

„ XII. Temperature Observations 

off Largybeg, . . 47 

„ XIII. Temperature Observations 

off Brodick, . . 48 

Cross Sections in East Arran Basin, . 48 

Table XIV. Temperature Observations 

off Garroch Head, . 51 

„ XV. Rate of Change of Temper- 
ature off Garroch Head, 52 
„ XVI. Average Daily Rate of 
Heating and Cooling off 
Garroch Head, . . 53 



160 



DR HUGH KOBERT MILL ON THE 



PACE 

The Arran Basin — contd. 

Seasonal Change of Temperature, Gar- 

roch Head, .... 53 

Table XVII. Temperature Observa- 
tions in Inchmarnoch 
Water, . . 56 

„ XVIII. Temperature Observa- 
tions oft' Ardlamont 
Point, . . . 56 

„ XIX. Temperature Observa- 
tions off Skate Island, 57 
Rate of Daily and Hourly Tempera- 
ture Change, Skate Island, . . 58 
Cross Section at Skate Island, . 60 
Seasonal Temperature Changes at 

Skate Island, ... 61 

Table XX. Typical Vertical Tempera- 
ture Curves off Skate Island, . 61 
Relation of Density to Temperature 

Change, .... 63 

Table XXI. Temperature Observa- 
tions off Kilfinan Bay, . 64 
„ XXII. Temperature Observa- 
tions at Otter I., . 65 
Temperature Sections of the Arran 

Basin, .... 66 

Particulars of 18 Axial Sections, Chan- 

nel-Cuill, .... 66 

Compound Sections, radiating from 

Inchmarnoch, ... 69 

Seasonal Range of Temperature in 

Arran Basin, ... 70 

Table XXIII. Monthly Mean Temper- 
ature of the Mass of 
Water in the Three 
Divisions of the Arran 
Basin, from Curves, . 70 

Loch Fyne — 



Table XXIV. Temperature Observa- 




tions at Otter II., 


73 


Surface Observations at Otter, . 


74 


Table XXV. Temperature Observa- 




tions off Gortans Pt., 


75 


„ XXVI. Temperature Observa- 




tions at Minard and 




Paddy Rock, . 


76 


„ XXVII. Temperature Observa- 




tions off Furnace, 


77 


„ XXVIII. Temperature Observa- 




tions off Strachur, 


7!) 


„ XXIX. Temperature Observa- 




tions off Inveraray, . 


80 


Rate of Daily and Hourly Tempera- 




ture Change at Strachur and Invera- 




ray, ..... 


80 


Cross Section at Inveraray, 


82 


Table XXX. Typical Vertical Tem- 




perature Curves in 




Loch Fyne, . 


S3 



Loch Fyne — contd. 

Seasonal Range of Temperature at 

Strachur and Inveraray, 
Table XXXI. Temperature Observa- 
tions at Dunderawe, . 
„ XXXII. Temperature Observa- 
tions at dull, 
Temperature Sections of Loch Fyne, . 
Particulars of 23 Sections, 
Table XXXIII. Density of Water, in 
situ, in Loch Fyne, 
„ XXXIV. Bottom Salinity and 
Temperature at 
Strachur, 
Seasonal Variations of Temperature in 
the Mass of Water in Loch Fyne, . 
Table XXXV. Mean Temperature at 
Various Depths in 
Loch Fyne, . 
„ XXXVI. Average Change of 
Temperature per 
diem in Loch Fyne, 
„ XXXVII. Mean Annual Tem- 
perature of Air 
and Water for Loch 
Fyne, 
Gareloch — 

' Table XXXVIII. Temperature Obser- 
vations at Row I., . 
„ XXXIX. Temperature Observa- 
tions at Row II., . 
„ XL. Cross Section of Gare- 

loch at Clynder, . 
„ XLI. Temperature Obser- 

vations at Shandon, 
Typical Gareloch Temperature Curves, 
Partial Cross Section at Shandon, 
Table XLI I. Temperature Observa- 
tions at Gareloch- 
head, 
Temperature Sections of the Gareloch, 
Particulars of 19 Sections, 
Evidence as to Circulation of Gare- 



loch, 
Table 



XLIII. Mean Temperature of 
Vertical Soundings, 
Gareloch, . 
XLIV. Mean Temperature at 
Various Depths in 
the Gareloch, 
XLV. Period of Heating and 
Cooling, and Daily 
Rate of Change of 
Temperature in the 
Clyde Sea Area, 
XLVI. Mean Annual Tem- 
perature of Air and 
Water for the Gare- 
loch, 



TAGE 

83 

86 

88 
90 
90 

92 

98 
98 

99 

101 

103 

104 

105 

106 

108 
108 
109 



110 
111 

111 

115 



118 



118 



120 



121 



CLYDE SEA AREA. 



161 



PAGE 

Loch Goil — 

Table XLVII. Temperature Observa- 
tions off Dog Rock, . 123 
„ XLVIII. Temperature Observa- 
tions at Loch Goil- 
mouth, . . 124 
Temperature Observations off Carrick 

Castle, . . - .124 

Table XLIX. Temperature Observa- 
tions off Stuckbeg, . 125 
„ L. Typical Vertical Tem- 
perature Curves, 
Stuckbeg, . . 126 
„ LI. Temperature Observa- 
tions at Loch Goil- 
head, . . 128 
Temperature Sections of Loch Goil, . 128 
Particulars of 17 Sections, . . 128 
Table LI I. Mean Temperature at 
Various Depths in 
Loch Goil, . . 132 
„ LIII. Average Change of Tem- 
perature per diem 
in Loch Goil, . 134 
„ LIV. Mean Annual Tempera- 
ture of Air and 
Water for Loch Goil, 135 
Loch Strivan — 
Temperature Observations at Clapoch- 

lar, ..... 136 

Temperature Sections of Loch Strivan, 
Particulars of 23 Sections, . . 137 

Seasonal Variation of Temperature, . 137 

Table LV. Period of Heating and 
Cooling, and Daily 
Rate of Change of 
Temperature in Loch 
Strivan, . . 141 

„ LVI. Mean Temperature at 
Various Depths in 
Loch Strivan, . 142 

„ LVII. AverageChange of Tem- 
perature per diem in 
Loch Strivan, . . 143 

„ LVIII. Mean Annual Tempera- 
ture of Air and Water 
for Loch Strivan, . 144 



The Dunoon Basin — 
Comparison of Observations at Dog 

Rock and Gantock, . 
Table LIX. Mean Temperature at 
Various Depths in 
Dunoon Basin, 
„ LX. Average Change of Tem- 

perature per diem in 
Dunoon Basin, 
„ LXI. Period of Heating and 
Cooling, and Daily 
Rate of Change of 
Temperature in 
Dunoon Basin, 
„ LXIT. Mean Annual Tempera- 
ture of Air and Water 
for Dunoon Basin, 
General Summary — .... 
Temperature Conditions of the Clyde Sea. 
Area, .... 

Table LXI II. Monthly Mean Tem- 
perature of Surface 
5-Fathom Layer in the 
Divisions of the Clyde 
Sea Area, 
„ LXIV. Monthly Mean Tempera- 
tures of the mass of 
Water in the Divisions 
of the Clyde Sea Area, 
„ LXV. General Summary of 
Temperature Condi- 
tions in the Clyde Sea 
Area, 
Thermal Classification of the Divi- 
sions, .... 

Heat Transactions of the Clyde Sea Area, . 



Specific Heat 

Water, 
Table LXVI. 



PAGE 



145 



146 



147 



148 



and Density of Sea- 



Total Heat Changes in 
the Water of the Clyde 
Sea Area, 
,, XLVII. Heat-storing Power of 
the Divisions of the 
Clyde Sea Area, 
Estimate of Heat Gained and Lost by 
the Area as a Whole, 
Contents and Summary, .... 



148 
149-158 

149 



150 

152 

153 

155 
155 

1 55 
156 

157 

158 
159-161 



VOL. XXXVIII. PART I. (NO. 1). 



Dc.Eim- r Vol.JXXVHr 



PLATE I 



NEGRETTI & ZAMBRA'S DEEP SEA THERMOMETER 
IN THE SCOTTISH FRAME. 



Fig. 2. REVERSED 



Fig. 1. SET 




A Thermometer Case. 

o Groove In top of case. 

B Pivots on which case rotates. 

o Set-screw to prevent pivots working 
loose. 

C Pin holding case erect. 

V Lever raising pin and letting thermo- 
meter reverse. 

E Spiral spring keeping pin in place. 

F Indlarnbber band to start thermometer 
when pin is withdrawn. 

O Flat brass spring. 

H Point attached to O to secure thermo- 
meter in inverted position. 

h Boss in which H fits.* 

/ Vice, securing thermometer frame to 
line. 

J Ram's-horn attachment securing line to 
lower part of frame. 

K Messenger suspended by wire to groove a. 

L Messenger from above striking iX which 
raises and lets A reverse, K being 
cast loose to descend to next ther- 
mometer. 

M Forked piece on which D rests, and 
through which the sounding line 
passes freely. 

m Split pin to prevent sounding line slip- 
ping out of fork M. 

* The damping arrangement shown here is 
now superseded by a more satisfac- 
tory form, devised by Messrs. Negretti 
& Zambra. 



K 



• 



B artliolomaw. EdinT 



jy. Soc. Edm r Vol.JOXVlJI 
Fig. 1 



1886. 



TEMPERATURE VARIATIONS 

SKATE ISLAND. Appan Basin Central. DEPTH AND TIME. 

1887 poor 



PLATE II 



Faths 0< 



MAR APR MAY JUN. JUL. AUG. SE P OCT NOV. D EC JAN. FEB. MAR APR. MAY JUN. JUL AUG. SEP OCT NOV DEC JAN. FEB MAR APR MAY. JUN. JUL AUG SEP OCT. 






• ■on 


Bff 




C ,4 - T0 


56" 




52* - 


54- 




50?- 


52' 




4ff- 


SO* 




46°- 


48' 




++•'- 


46" 




42"- 


44* 




40*- 


42' 


I: 


• 1U>« 


40* 



Faths o 



Fig- 2 PLATEAU Temperature with Depth and Time. Hourly Observations. 

June 1 1887. June 18. 1887. 

20** 2lh 22 h. 23h 24h 1 h oh 3 h 4 h 



6h 7h 




5J4h.f aw. I h <■ 2he 3 h.e. 4h.R 5he <- w. I h.f 2hf 3h.f. 4 h f Shf 



Bartholomew. Eoia 1 



oy Soc.Eairi r Vol.Z2XVni 



Tig. 3 

1886. 



TEMPERATURE VARIATIONS 



GARROCH HEAD. N.E. Arran Basin DEPTH AND TIME. 

1887 



PLATE III 



Fath* -, MAR APR MAY JUN ' JUL AUG - SER 0CT N0V DEC JAN - FEB MAR - APR MAY JuN JUI - AUG - SEP 0CT N0V OK JAN.' FEB MAR. APR MAY. JUN. JUL AUG SEP OCT NOV r ,. 

tn?0 ' fi \ v\" ~\h\u:vw r ] ini\w/ iiww/flw \ \\\\\\\\vxy/\W7 7 / iiiwwha irnim mi-// // , / ' ° Fath5 





Scm.1 f Colouring 

for mperature 

■ I 





TO 56" 




54 






•- SO- 




■'- 48* 




•- 46* 




■'- 44' 




■ ' - 42° 




.ow4C 



Faths o 



Fig .4 STUCK BEG. Loch Goll. DEPTH AND TIME. 

1886. 1887. I 888 

APR MAY JUN JUL. AUG. SER OCT NOV. DEC JAN. FEB MAR. APR. MAY JUN. JUL. AUG. SEP OCT NOV. DEC JAN. FEB MAR. APR MAY JUN. JUL. AUG. SEP. OCT. 




Faths 



Bsu-tlioloTni^v. Edin5 



Icy. Soc. EchiL r Vol. XXX VIII 



TEMPERATURE VARIATIONS 



PLATE IV 



Kg. 5 

Days from I^Jan.1886 200 



LOCH FYNE. MEAN RATE OF CHANGE OF TEMPERATURE. Per diem. 

300 400 500 COO 




MAY. 86. JUNE. JULY. AUG. SEPT OCT. NOV. DEC. JAN.87 FEBY. MAR 



JUNE. JULY. 



OCT NOV. DEC JAN 88. 



g-6 

is from I sfjan. I88S 200 



LOCH GOIL. MEAN RATE OF CHANGE OF TEMPERATURE. Per diem. 

300 400 500 COO 




MAY.86. JUNE. JULY. AUG. SEPT OCT NOV. DEC. JAN.87. FEBY. MAR. APR. MAY. JUNE. JULY. AUG. SEPT OCT NOV. DEC. JAN 88 FEB. MAR. 



Scale of Colouring 



TOR TEMPERATURE 


54° TC 


56' 


ssr- 


54- 




52" 




SO" 


46"- 


48° 


44 - 


46* 


42*- 


44" 


40* 


42* 


BELOW 


40* 



Fig 7 CHANNEL. Mull of Cantyre or South of Sanda. DEPTH AND TIME. 

1886. 1887 , 888 . 

MAR APR MAY JUN. JUL. AUG. SEP OCT NOV. DEC JAN. FEB MAR. APR MAY. JUN. JUL. AUG. SEP OCT NOV. DEC JAN FEB MAR APR MAY. 
Fathso VSKZ/ 1 




14- 1 4>Q? 



30 



60 

Bartholomew, Edm^ 



3oc. Elm 1 Vol. X XX V.LLL. 



PLATE V 



TEMPERATURE VARIATIONS 



Fig. 8 STRACHUR. Loch Fyne. DEPTH AND TIME. 

1886. 1887 1888. 

MAR APR MAY JUN. JUL. AUG. SEP OCT. NOV. DEC JAN. FEB. MAR. APR. MAY. JUN JUL. AUG. SEP OCT. NOV. DEC JAN. FEB MAR. APR MAY. JUN. JUL. AUG SEP. OCT. 



bso 




Faths 



Fig. 9 SHANDON. Gareloch. DEPTH AND TIME. 

1886. 1887 1888. 

APR MAY JUN. JUL. AUG. SEP OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY JUN. JUL. AUG SEP OCT NOV. DEC JAN. FEB MAR APR MAY JUN JUL AUG SEP. OCT. g path? 



f TURC 




B artkolomew E3iD r 



/ 



t. Soc. Eton? Vol. XETOE. 



TEMPERATURE VARIATIONS 



PLATE VL 







Faths o 



Fig 12 CLAPOCHLAR. Loch Strivan. DEPTH AND TIME. 

1886. 1887 1888 

APR MAY JUN. JUL AUG. SEP OCT NOV. DEC JAN. FEB MAR. APR. MAY. JUN JUL. AUG. SEP OCT. NOV DEC JAN. FEB MAR APR MAY. JUN. JUL. AUG SEP. OCT. 




*3 



Soc.EaitfrVol.ZXXVTII 



VERTICAL TEMPERATURE CURVES 

AT DIFFERENT SEASONS. 



Skate Island. 1886-87. 

43 44 46 46 47 48 49 BO 51 52 53 54 



Fig. 14; Skate Island. 1887-88. 

43 44 45 46 47 48 49 50 SI 52 53 54 55 



PLATE VII 



Fig. 15 Skate Island. 1888. 

42 43 44 45 46 47 48 49 50 51 




Faths 



rachur — Inveraray. 1886-87. Fig. 17 LOCH FYNE. Strachur — Inveraray. 1887 1888. Fig 18 LOCH FYNE. Strachur - Inveraray. 1888. 

47 48 49' 50 51 52 53 54 55 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 43 44 45 46 47 48 49 50 SI 52 53 54 55 56 57 58 











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LCH GOIL. Stuckbeg. 1886.-87. 

VS!** 45 46 47 48 49 50 SI 52 53 



Fig .20 LOCH GOIL. Stuckbeg. 1887.-88. 

43 44 45 46 47 48 49 50 51 52 S3 54 



Fig. 21 LOCH GOIL. Stuckbeg. 1888. 

43 44 45 46 47 48 49 50 SI 52 53 54 55 56 

yj fms 




Bartholomew. Kdin T 



Soc.EiirfYoIXSXVin 



PLATE VUI 



TEMPERATURE SECTIONS OF CLYDE SEA AREA 

FROM THE CHANNEL THROUGH THE WEST AND CENTRAL ARRAN BASINS TO CUILL, LOCH FYNE 







BarLkolomew Eclm? 



soc. Edm? Vol. xxxvm 



PLATE IX 



TEMPERATURE SECTIONS OF CLYDE SEA AREA 

FROM THE CHANNEL THROUGH THE WEST AND CENTRAL ARRAN BASINS TO CUILL, LOCH FYNE 






Bartholomew; E<Hin r 



j. Soc.Eain r Vol.2SXVIir 

TEMPERATURE SECTIONS OF CLYDE SEA AREA 

FROM THE CHANNEL THROUGH THE WEST AND CENTRAL ARRAN BASINS TO CUILL, LOCH FYNE 



PLATE X 







Bartholomew. Edir. 1 



Soc. Eiu£ Vol. XX XV1H 



PLATE XI 



TEMPERATURE SECTIONS OF CLYDE SEA AREA 

FROM THE CHANNEL THROUGH THE WEST AND CENTRAL ARRAN BASINS TO CUILL. LOCH FYNE 







Bartholomew. Eclip? 



y 



>oc.Eaii£ Vol xram 



PLATE XII 



TEMPERATURE SECTIONS OF LOCH FYNE 







boo 





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Soc.Edirf VolXXXWE. 



PLATE Xni 



TEMPERATURE SECTIONS OF LOCH FYNE 




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PLATE XIV 



TEMPERATURE SECTIONS OF LOCH FYNE 















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SocEta? VolXXXVDI 



PLATE XV 



TEMPERATURE SECTIONS OF LOCH FYNE 





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B arQioXaiaew J£ 3ua,T 



.Eaia r Vol.Z22Vm 



PLATE XVI 



TEMPERATURE SECTIONS OF GARELOCH 












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Bartholomew, E3iu.? 



TEMPERATURE SECTIONS OF LOCH GOIL 



PLATE XVII 











11 


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Bartholomew, E4ii r 



.."■ 



Soc.EcLm r Vol.XXXVnr 



PLATE XVUl 



TEMPERATURE SECTIONS OF LOCH GOIL 



rite^ 





i 



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nj 


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ai 


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to 


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ul 




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v , , V- ,- — , — , — , — -Z^ 


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BarfliolOTiiew. Bdiitf 




&?/ ■■■■../ 



.Editr 1 ? vbizxxvnr 



PLATE XIX 



TEMPERATURE SECTIONS OF LOCH STRIVAN 






if V 






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1 


6 >b 6 Ji o 




n o u> 








IX w (■> <•) * * 


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B artL-olomew. Edii 



Soc.EiuSYol.UaViU 



PLATE XX 



TEMPERATURE SECTIONS OF LOCH STRIVAN 



























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b 






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Bartholomew, EdiiLt" 



' 



PLATE XXI 




Soc.Edin? Vnl XXXVIIj 



TEMPERATURE CURVES 



PLATE XXn 



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o 

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Bartb.olom.ew. Ecliii r 



y} oc. Eim. r Vol. XXXVIII 



PLATE XXIII 



TEMPERATURE CURVES 



Fig. 4 CHANNEL— TYPICAL CURVES. 

41 42 43 44 45 46 47 50 51 52 53 54 55 56 

V 



Fig. 5 MINCH AND NORTH ATLANTIC TYPES. 



16 4 86 






(I 



8*12 87 I2 6-6G 




Ft? 



87 



Fms 



46 47 48 49 50 51 52 53 54 55 56 S7 











a/ 












B 


















































to 






















7 
















































/ 






















fr 














'29 


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y 






























































































































1887 



















£ 6 CHANNEL— SEASONAL VARIATION OF TEMPERATURE OF MASS OF WATER, AND AIR AT MULL OF CANTYRE LIGHTHOUSE. 



Temp. 60' 



1887. 
MAR. APR MAY JUN JUL AUG. SEP OCT. NOV DEC. JAN FEB MAR. APR. MAY JUN JUL AUG. SEP OCT NOV DEC. JAN. FEB. MAR. APR. MAY 





































































































































































































































































































^ 


V 
















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. 










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v > 


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\ 


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K**n 
























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-' 


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i 












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60 Tern p. 
58 
56 
5+ 
52 
50 
48 
46 
44 
42 
40 
38 
•10 



-•05 
10 



Curve of Rate of Change of Water Temperature in degrees per day (averages per month) 



Fig. 7 PLATEAU, WEST.— TYPICAL CURVES. 

J 41 42 43 44 45_ 55 46 47 48 43 




Positive Slope, 

Heating 

N93. 



Homothermic Curve, Negative Slope. Homothermic Curve, 

Maximum, Cooling. Minimum, 

N°23. N?I0 N°32 



Fms 
5 




Fig 8 PLATEAU, CONTORTED VERTICAL CURVES. 



B artholomew. Edin? 



5oc.Edm r Vol. JUa VILE 



PLATE XXIV 



TEMPERATURE CURVES AND SECTIONS 



Fig. 9 PLATEAU, WEST. Hourly Observations— Curves for Various Depths. 



Dat 

Temp 59 

58 
57 
56 
55 
5+ 
53 
52 
51 


e- June 17 
Hour 20. 


1887. 

21 


22 


23. 


June 




18. 




2 






4 


5. 


6. 




7. 


8 


59 Temp 








1 ^S 


^e? 










































58 




















































57 




















































56 






















































55 























































5+ 




















































53 




















<jr '' 


— - 


•-- 






























52 




»— 


§Jm 


horns 




_-*-- 





■*'- 


r'' 




















~~ 


---- 


— - 


-- ~ 


J-—— 


— - 


— — 


51 






Mea 


n 




— - 




, 








































,.•' 








■.....■" 


















50 
+3 
48 


50 








K> 


^*%i 


«»•••• ■ 






































48 
48 

7t 






8o 


Wom^y2Z-Tl Fathoms 


























., 




... 











H W. 


_J 
































i 
















! 1 i r~"-i 










— -T-— T ] ' 







Fig 10 PLATEAU, WEST. Vertical Curves 

43 50 51 52 53 54 55 56 57 58 59 

T.S o - ~t - -* - r — — * ° TIT'S 







A^ 


-<^ rr ~ 


••■-; 




■^-^ J 




c," 




-f"" 














_ .. 


; 






















f 1 

:1 


k- 


7 - 


21 K 
23' 
7* 


— 

— 
— 


H.ghT 
2H<s e 
4H»f 


de. 
bb 

D0(j 








j 

1 














©18 6 67 






.. 









Fig. 12 Rough Section— Brodick to Irvine, 20th September, 1887. 

Brodick (Not drawn to scale.} 



56* 565 



eg, Fms 




All Exceptional Curves, Largybeg. 

47" 48' 49- 50- 5f 52 - 53 - 54' 55" 56* 57" 



Fig. 13 




FT 1 ? FT 1 ? o 



Change of Slope at Maximum. 
Garroch Head 

49 50 51 52 53 54 55 



S 
10 






[ 
































. 






















^A 
















1 










/ 




\ 








1 












1 














/ 














60 
















1a 










J 




3¥es 








4 

29^ 


86 





Fig. 14 

Cooling Curves, Negative Slope. 

Garroch Head 



42 43 44 45 46 47 48 49 50 51 



'?U 








1\ « 


\ 






10 








\ ': \ 






i 










\i 


\ \ 










20 








1 




1 


• 


















1 
I 


i 






30 
40 












1 

1 
t 
















! 






1 

1 

- 1 ■ 


\ 




















1 




\ 
\ 
\ 


















1 
1 
1 




\ 
\ 
\ 

\ 

\ 




50 
















1 


















! 
1 
1 




\ 

I 










E 


Id 




IC 


"" 1 
1 
IE 




i 
JA 










1 187 


(13) 

27'|'Z8£ 


f.12 


) (L!) 

!6 ill 12-86 




i,0) 
2 12*6 



F 1 ?? 



Bartholomew, E3in5 



Soc.Eim? Yol.XX_X.ViiI 



PLATE XXV 



TEMPERATURE CURVES 



Tig. IB- 
MAXIMAL CURVES. Positive Slope. 
Qarroch Head 

48 49 50 51 52 53 54 55 56 57 58 













1 

t 
1 






































1 
1 




















1 














// 






1 
1 

1 














/ 






1 
1 
1 


















/ 
/ 
















/ 
/ 












1 






T 










1 


. 






1 












. j 


! 




I 
1 
1 










A© 


IS 87 J&®\6 


887 


0<g 


20987 









F^? 



Fig. 16. 

Warming Curves, at Minimum. 
Qarroch Head 

41 +2 4-3 44 

pms 







I 7 

/ 

* 




\ 


/ 


7 




1 








i 












I 




, 
















1 

i . - 








i 
1 








1 
1 - 








1 

1 








i 






kkTAs: 


' f »'«. 


" 



Fig. 17 
Curves for 12. August. 1887 
Inchmarnoch & Ardlamont. 



46 47 48 49 50 51 52 53 54 55 















,- - ■ 










































































































1 










A 


rdlanont 


c 
























































50 

60 
,0 
80 












































/ 
































/ 




























1 


















y Inchmarnoch 













Fm$ 



Fig. 18. 

RTICAL CURVES. Skate Island. 
15 & 16 June. 1887. 

47 48 49 50 51 52 53 54 















■*B 


pms 






j 


1 /> 


1 








/ 


























lb 




■ 
















1 












ib 


i 




















Jb 


I 
























1 








i 
\ 






























| 


. . 












\ 




















































• 




















. 


















1 








A 

7 " 


1 . J 












13 


3 













Fig. 19. 

VERTICAL CURVES. Skate Island. 
7. «, 8 July, 1887. 

46 47 48 49 50 51 52 53 54 55 













^ 


©' 


/-'' 


■ 










1 


f ^~ 








1 
1 


















/ 
/ 
/ 
















/ 
















/ / 


f 
















i 


















i 














I 

// 


















/; 
// 
/ / 


















i i 

i 


















I 
i 


























































































































, 
















































i 









F"P5 o 



Fig. 30. 
VERTICAL CURVES. Skate Island. 
I4-& 16. August, 1887. 



47 48 49 50 51 52 53 54 55 56 _ 



5P 



! 










% 


a[ 


<'' 


V23); 














/ / 


' 




— 








/ 


/ 


/ 
















/ 
/ 


•f 














1/ 


■ 














/ 
/ 1 
















/ / 
















/ / 
















/ / 


















i 
i 


















i 
i 














! 
\ 


















1 
1 


















1 
1 


































/ 
t 


















/ 
i 
i 


















i 
i 


















i 
i 
















- 

! 


i 















pms 



Bartholomew, E3in3" 



ic.Eim? Yol.JOX.ViiL 



PLATE XXVI 



TEMPERATURE SECTIONS AND CURVES 



+5 4-6 +7 48 



Kg. 31. 
VERTICAL CURVES. 

Skate Island. 
247 January. 1888 ' 



<m'< 


t 






1 














1 


i 


\ 




1 

H 


' 


\ 










i 










A 








\\ 
























































j- 










4 




- 








— 




B 


®, 











Fms 



Fig. 22 CROSS SECTION -Central Arran Basin. 
Through Greatest Depth. 
23 September, 1887. 
















I00 






i in 







Fms o 



Fig. 23 ARRAN BASIN, COMPOUND TEMPERATURE SECTION JUNE. 1887 

Western Central Eastern 

I S I 



— T-* 

52 












^F= 


=±3 






— 




— i — 


i 51 


j 








































J _ 




*^£0 









ta 






































S2-. 




























. +7 























































— 




«. 








































47. 




















































































































































46 




























































IS 






































































































^/i X y | \ 


































































X\ i 




1 1 l\ 














- 
















■ 


c \ 


4 i 


c 


>A 




\ 






























' 


/ 


y 


H 


3 














^C ^N4*~ 


1 \ 


/ ' '' 


1. 1 

I 


>^l\ 


j \ 


/l 


n 




jA 


J | 


• 1 ^ 





Ffp? 



Miles 18 15 12 



12 15 18 Miles 



E arth.olomevr, Edui* 



Soc.Eiiii r Vol. XXXV11L 



PLATE XXVII 



TEMPERATURE SECTIONS AND CURVES 



Fig. 24 ARRAN BASIN, COMPOUND TEMPERATURE SECTION- September, 1887 

Western Central Eastern 

I S I 





I 5SJ__ — | 












/ 


\ 


\ 






































\ 


\ 








■ 55^ 








- 






54- 




























^ 








































^ 














53 








|\ 




























































53_ 








- 






















































































52 






























52 


























^ 






























































_5_L_ 


















f 


























































50_ 
















































































/l |\ 


















49 










\& 
























v n 


















\ 




T\ 


A 


j W 1 


t 1 1 1 1 '1 1- . 1 IT > i 



Miles 18 15 



IS 18 Miles 



Fig 25 -ARRAN BASIN, Seasonal Variations of Temperature of Water and Air. 



n?G0 
58 
56 


1886. 1887. 1888. 

MAR. APR MAY JUN. JUL. AUG. SEP OCT NOV. DEC. JAN. FEB. MAR. APR. MAY. JUN. JUL. AUG. SEP OCT. NOV. DEC JAN. FEB MAR. 


APR. 


MAY. JUN. JUL. 
















/ \ 




















































I 







































\ 




















s* 






















52 
50 
48 
+6 










/Pfc\ 






















v K 














/ 










1 ¥ y^t\ 






1 ' s 


' — *s 




/ j 




/ 1 ? LAf \ x 












V 
V 
























\ 










/ 










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^^^^ 


/ 
if 


/y 














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^ 










42 

+0 
38 


""/l ^s 






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^ 


-.Jjf- 
















rH- 


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1 




1 X^\ I 






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y 


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l 










\ i \ ' / 














































— 




































































+ 05 
































































— * 





""*■» 


v 
















4?~~ 





■»«.. , 






























/ 










V 


\ 










/ 


y 








"N 


\ 














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r 












/ 












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N 


\ 












/ 


























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s.-> 


/ 


















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i 





Curve of Rate of -Change of Water Temperature in degrees per day (averages per month) 



60 Fms 
56 

56 

54 

52 

50 

48 

46 

44 

4-2 

40 



+ •10 

+ 05 



-05 

■10 



Barth-olomevr. E3inT 



E4iii r Vol.XXXVIiL 



PLATE XXVUI 



TEMPERATURE CURVES 



26 OTTER 1 1 .Typical Curves- 

♦5 46 52 53 54 

__ 



Kg. 27. GORTANS -Typical Curves. 

45 46 47 48 49 50 51 52 53 54 55 56 50 51 52 53 54 55 56 





Fig 28. FURNACE -Typical Curves. 

6 47 48 49 50 51 52 53 54 55 



46 47 48 




Ft? 



Fig. 29. STRACHUR, 
Curves for 19 & 20. April, 1886. 

41 42 43 



Fms o - '^TT.. 1 F m s 

!l9-4-86(T)l /(2', 

I p 10 4 86 
. f 



Fig. 30. STRACHUR, 
Curves for 5 8c 7 November, 1887. 



Fms 



45 46 47 48 49 50 51 



S-II- 


B7 








Cf 7 ) 

7" II 87 










% 








































































fl 












)' 








f 


V 










' 










l 










f 












/' 



















F^s 



g 31. STRACHUR R ? 32 - 'NVERARAY 

ivca p 161,18 October, 1888. Curves for 16. & 17. September, 1886. 

■ 46 +7 48 49 50 51 46 44 45 46 47 48 49 50 51 52 63 54 55 

-I pms F"«o 
























/ 




















/ 


/ 










- 












r 


7- 














,'V 
























.'S' 






















^ 






















y^- 


-' 




















I6986 


f I 


























1 J 
1 1 














































































f©' 7 


■9 86 























Fig 33. INVERARAY 
Curves for 27 th September, 1886. 

44 45 46 47 48 49 50 51 52 53,- 

pms Fms o r— -■— *- I 





















I 






































































































































































































































B artL.olcrm.ew, EdinT 



jc.Edm r Voizxr7nr 



PLATE XXIX 



TEMPERATURE CURVES 

LOCH FYNE 



Fig. 34. INVERARAY 
Curves for 25 & 27 August, 1888. 

44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 



- 






















- ~X^ 


**"- 




• 


© 

Sr 8-88 
















,'''' 


<■*** 


























--& 




y 


























































f r s 


**" 


278 


58 


























// 
































A 


































if 
































/ 


I 
































jl 


































ij 

































































































































F m ? 



Fig. 35. INVERARAY 
Curves for 26 August and 3 September, 1888 

45 48 47 48 49 50 SI 52 53 54 55 

FfT?0 — — . - —z~\ 9 Fms 





















^~ 




10 














































20 














































30 














































40 














































50 


























(3-989 






















@ 26 889 

















Fig 36. DUNDERAWE-Typlcal Curves. 

43 44 45 46 47 48 49 50 46 47 48 49 50 51 





















**- 






J 


G 






i 




























\ 
























































A 




















1 I 










\ 


















\ 










\ 


















X 






10' 


IS) 
587 


■J) 
5 2-87 






17-11-86 












5 1187 





pms FT»S 



Fig 37. DUNDERAWE-Typlcal Curves. 

44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 81 







































































































































































/ 




























/ 






























248 88 


25 : 8 


88 








1 



















Fms 



Fig 38. CUILL -Typical Curves. 



Fms , 
5 I 
10 

15 



42 47 48 49 50 51 52 53 54 55 56 57 58 59 60 38 39 40 41 42 43 44 45 46 47 48 



Lfl \U 






— 








1 










-"« 
























r 














































\ 1 / 














































CD ® @ 

20 4-86 8 7 87 17 10 88 


. 




































1712 


i7 



Fig. 39 
sttage in Hypothetical Circulation of Water by up-loch Wind. 



m*- 







V 


farm 














♦4- 






!>/ 








< h 








■1 ' 








os^-<^ 




j 








"^^^^^ / ^ 




^l 


. J.:. . 


' 





Fig. 40 
Hypothetical circulation of Water by long continued up-loch Wind. 

I* r^m — > 



s 




Cool 












> : 




/ 


( 










\ 


^ 














>[ 






^0**T^ 





EarttLolomew, E3in5 



-ir.. "Mm r Vol XX X VI II 



PLATE XXX 



TEMPERATURE CURVES 



Fig. 41 LOCH FYNE Seasonal Variations of Temperature of Water and Air. 





1886 1887. 1888. 

MAR APR MAY JUN. JUL. AUG. SEP OCT. NOV. DEC JAN. FEB. MAR. APR. MAY JUN. JUL. AUG. SEP OCT NOV. DEC. JAN. FEB MAR. APR MAY. JUN. JUL. AUG. SEP. 




















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PLATE XXXI 



TEMPERATURE CURVES 



Fig. 45. 
isverse Section of Gareloch at Clynder. 




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Fig. 47. GARELOCH -Seasonal Variation of Temperature of Water and Air. 

1886. <887 1888. 

MAR APR MAY JUN. JUL. AUG. SEP OCT NOV. DEC JAN. FEB MAR. APR. MAY. JUN. JUL. AUG. SEP OCT. NCV DEC JAN. FEB MAR. APR MAY. JUN. JUL. AUG. SEP. 



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1887 1888. 

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Barli.olomew. E3in?* 



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PLATE XXXR 



TEMPERATURE CURVES 



■]jig. 49 LOCH STRIVAN-Seasonal Variations of Temperature of Water and All-. 

1886. 1887. 1886. 

MAR. APR MAY JUN JUL AUG. SEP OCT. NOV DEC. JAN, FEB. MAR. APR MAY JUN JUL AUG SEP. OCT NOV DEC. JAN. FEB. MAR. APR. MAY JUN JUL. AUG SEP OCT 



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B artkolomew. EdinT 



( 163 ) 



II. — A Fundamental Theorem regarding the Equivalence of Systems of Ordinary 
Linear Differential Equations, and its Application to the Determination of the 
Order and the Systematic Solution of a Determinate System of such Equations. 
By George Chrystal, M.A., LL.D., Professor of Mathematics in the University 



of Edinburgh. 



(Read 18th February 1895.) 



Systems of ordinary linear differential equations are of great importance, both from 
a practical and from a theoretical point of view. They figure largely in dynamical 
problems ; and Jacobi has shown that the general problem of determining the order of 
any system of ordinary differential equations whatever can be reduced to the problem of 
determining the order of a linear system with constant coefficients. Nevertheless, the 
present state of the theory of such a system still leaves something to be desired. It is 
true that a logical and systematic process for the solution was given by Cauchy. This 
consists in first replacing the system by another in which only first differential co- 
efficients occur, by introducing as auxiliary variables the successive differential coefficients 
of the various dependent variables up to the highest but one, and then reducing this 
system to the "normal form" by calculating the differential coefficients as linear 
functions of the dependent variables. It happens, however, when we attempt to do 
this, that we are led to a system consisting partly of differential equations of the form 

^=f r (, v ; x,)+g t (t) r = l, 2, ,s. . . . (1), 

where f denotes a linear function of x v . . . ., x s , partly of a number of non- differential 
equations connecting the remainder of the variables with x v . . . ., as g . The order of the 
system — that is to say, the number of independent arbitrary constants required for 
its complete solution — is the number of differential equations in the normal form ; but 
no rule is readily deducible from the method for determining beforehand how many of 
the equations in the normal system will be differential equations, so that we cannot 
predict the order of the system without actually going through the labour of reduction. 
Moreover, the normal form is in practice often not the most convenient for the purposes 
of solution. 

Another method, the one which is probably more familiar to English mathematicians, 
consists in using what may be called the " characteristic equation " of the system. For 
example, let x, y, z be the dependent variables and t the independent variable, and let 
the system be 

f 1 (D)x+y 1 (J)) 1/ +h 1 (B)z = ) 

f 2 (D)x+y 2 (T))y + k 2 (D)z = 0[ .... (1) 

f 3 (B)x+ ffs (D)y+h i (J))z=0) 

VOL. XXXVIII. PART I. (NO. 2). Y 



164 PROFESSOR CHRYSTAL ON THE EQUIVALENCE OF 

where D stands for cl/dt, and f v f 2 , etc., are integral functions of D with constant 
coefficients. Then the conclusion is drawn from (1) that 

Ke = 0, Ky = Q, Kz=0 (2), 

where K is the determinant \f (D), g 2 (D), h s (D) | ; so that each of the variables satisfies 
the differential equation 

K£=0 (3), 

which we call the " characteristic equation " of the system, K being the " characteristic 
determinant." The system (2), however, is not equivalent to (1). Hence, if 

£=A X e K ^+ . . . .+A n c K nt 

be the solution of (3), (n being the order of that equation, and therefore the degree in D 
of the integral function K), it does not follow that 

n n n 

x = X A„e A »* , y = X B n e knt , z = 2 C w e A »i', 
ill 

containing dn arbitrary constants in all, is the solution of (2). To get rid of the 
superfluous constants the values of x, y, z are substituted in (1), and we thus get a set of 
equations of the form 

/, (\) \+ ffl (X x ) B^ (X x ) C 1 = , 

/ 2 (X 1 )A 1+5 r 2 (\ 1 )B 1 +7 i2 (X 1 )C 1 = 0V .... (4). 

/ 3 (X,) A, +g 3 (X x ) B. + h, (\) C 1 = ) 

&c. 

Since X is a root of the equation K A = 0, obtained by substituting X for D in K, the 
equations (4) are equivalent to any two of them. If these two be independent, and 
neither of them identical as regards A l5 B x> C 1? the ratios of A 1? B l5 C x are determined ; 
and, on the like assumptions for X 2 , . . . ., X n , the 3n arbitrary constants reduce to n. 
Even if all the assumptions made were generally true, this process could scarcely be said 
to be a very satisfactory proof that the order of the system is really n. In point 
of fact, however, as is well known, the assumptions made are not always true ; and, 
in particular cases, the equations (4) do not in fact determine the ratios of A 1} B l5 C r 
It is true that there are various ways in which the solution may be amended in particular 
cases, but no general process, so far as I am aware, has been given which amounts 
to a proof of the theorem that the order of the system is always the same as the 
order of the characteristic differential equation, i.e., the degree of the characteristic 
determinant. In his remarkable memoir, " De investigando ordine systematis aequa- 
tionum differentialium vulgarium cujuscunque" (Crelle's Jour. lx. 1865), Jacobi makes 
this theorem his starting-point ; but the proof which he gives begs the question, 
for it amounts to nothing more than what has just been sketched for the case of 
three dependent variables. 



SYSTEMS OF ORDINARY LINEAR DIFFERENTIAL EQUATIONS. 165 

The theorem in question is true ; but the difficulty in demonstrating it lies in 
the fact that although each of the variables satisfies the characteristic equation, all of 
them may not be general integrals of that equation. In fact, it may happen that 
no one of them is a general integral. This may be seen at once by supposing the 
integral system of (1) to have the form x=f(b, c, t), y = g (c, a, t), z — h (a, b, t), where 
a, b, c are arbitrary constants. In this case the order of the characteristic equation 
is 3 ; but the order of the differential equations which determine the separate variables is 
in each case 2. 

I propose in this communication to give a rigorous proof of the general theorem 
above referred to, by means of a simple theorem regarding the equivalence of systems of 
linear differential equations with constant coefficients, and to deduce a systematic 
method for solving determinate systems of this kind which does not introduce superfluous 
arbitrary constants, and is not subject to failure in particular cases. 

Necessary and Sufficient Condition that tivo Systems of Linear Equations with 
Constant Coefficients be equivalent. 

Let the dependent variables be x u . . . ., x n , the independent variable t, and let 
U r and V r be expressions of the form, 

(r, 1) x x + (r, 2)x 2 +.— +(r, n)x n + S r , 
[r, 1] ^ + [r, 2].x 2 + . - + [r, n]x n + T, , 

where (r, 1) (r, n), \_r, 1], . . . , [r, n\ are integral functions of D ( = d/dt) 

with constant coefficients, and S,. and T r are functions of t alone. 

Consider any original system of m independent equations (m > n). 

U 1= 0, , U w = (5). 

Let 

^=0, , V TO =0 (6) 

be a system of m independent equations " derived from " (5) — that is to say, possessing 
the property that every solution of (5) is a solution of (6). 

Since the derived system is linear with constant coefficients as well as the original 
one, any process of derivation must consist in operating on the equations of the original 
system with integral powers of D, multiplying the resulting equations thus obtained by 
constants and adding. Hence we must have 

y 1 =&Ui+ • •■ — +g m u m 

V 2 = J7 1 U 1 + ...... + Vm Ur, (7) 



V m — «r 1 U 1 + +K m V m 

where £ 1} . . . . , £ TO , , k x , K m are integral functions of D with 

constant coefficients. We may speak of these as the midtiplier- system which derives (6) 
from (5) ; and call the determinant 



166 PROFESSOR CHRYSTAL ON THE EQUIVALENCE OF 

A = | itf* Km | (8) 

the modulus of the system (6) with respect to (5). 

We shall prove that the necessary and sufficient condition that the system (6) be 
equivalent to (5) is that the modulus of (6) with respect to (5) be constant. 

In the first place, the condition is sufficient ; for, if 

I ~i-H 2 Km | 

be the reciprocal of the determinant A, we have from (7) 

AU 1 = E 1 V 1 + H 1 V 2 + . . . + K l V m 

AU m = E m V 1 +H m V 2 + . . . +K m V w . 

Hence any solution of (6) satisfies 

AU 1 = 0, , AU M =0. 

But, if A reduce to a constant, this last system is equivalent to (5), for A cannot vanish 
since the system (6) consists of m independent equations. The condition is also necessary ; 
for, if the system (5) be a derivative of (6), then there must exist a set of integral 

functions of D with constant coefficients, say £/, . . . . , £„/, , «•/, . . . , «■„/, 

such that 

U 1 -£'V 1 + f 2 'V 2 + +£ m 'V m (9). 

U m = /C 1 'V 1 + K- 2 'V 2 + .... +K m 'V m . 

If we substitute the values of \J U , U wl from (9) in the identities (7), then, 

since U-,, . . . . , U m are independent, we must have 

iii-2+i-2Vo+ +£«'*., =o 

il£m + %2Vm+ • • • . + £irt'f (a = ; 
Vi'£\ +V0V1 + • • • • +VmK 1 =0 
Viiz +V2V0 + ■ • • • +W*2 =1 

Vi^m+VzVm + • • . . +VmKm*=0 

(fee. &c. 
Solving the above systems we have 

£-S 1 /A,.& # -H 1 /A, , f-'-Kj/A 



K 



i' = H,„/A) /c 2 ' = H,„/A, . . . . , K m ' = K m jA 



SYSTEMS OF ORDINARY LINEAR DIFFERENTIAL EQUATIONS. 



167 



Hence 



A'=iliV • • • • Km'HKxH! 



K m |/ A "■ = A'" - 7 A" 1 = i/A 



Now, since £/, , k„/ are all integral functions of D , A' must be an integral 

function of D, and therefore also l/A ; but this is impossible unless A reduce to a con- 
stant. Hence the condition is not only sufficient but necessary ; and we have now the 
theorem in the form — 

When tivo systems of linear equations -with constant coefficients are equivalent, the 
modulus of either with respect to the other must be constant, and the converse is also true. 

This equivalence theorem can be expressed in another form, which is convenient for 

some purposes. 

The matrix 

(11) (12) (In) 



(ml) (m2) . 



{run) 



(10), 



whose m rows are made up of the operator coefficients of the dependent variables in the 
m equations of a system, may be called the Matrix of the System. 
From (7) we have 

[11] = (11)&+(21)£+ +(ml)| m 

[In] = (ln)g 1 +(2n)g 2 + + (mn)g„ l 

[21] = (11)7 ?1 + <21>,,+ +(ml) Vm 

[2n] = (ln) >ll + (2ii)>i 2 + +( / nin)ij m 

&c, &e. 



Hence we have 



[11] 
[ml] 



[In] 
[mri] 



(11) 
(ml) 



(In) 

(inn) 



(11) 



in the sense that every determinant in the first matrix is equal to the corresponding 
determinant in the second, multiplied by A . Hence 

The necessary and sufficient condition that two systems of linear equations with con- 
stant coefficients be equivalent, is that every determinant in the matrix of the one system 
differs by the same constant multiplier from the corresponding determinant in the matrix 
of the other. 

In particular, 

In order that two determinate systems {of n equations in n dependent variables) be 
equivalent it is necessary and sufficient that the determinants of the two systems differ 
merely by a constant factor — that is to say, that 

1 (11) (22) .... (nn) | = | [11] [22] .... [nn] | x const. 



108 PROFESSOR CHKYSTAL ON THE EQUIVALENCE OF 

This second form of the equivalence theorem enables us to test the equivalence of the 
systems directly, without calculating the system of multipliers. 

Reduction of any Determinate System of Linear Equations with Constant Coefficients 

to an equivalent Diagonal System. 

By a diagonal system is meant a system of the form 

[11>; 1 + [12> 2 + [13>3+ +OK+T 1 = 

[22> 2 +[23]r 3 + +[2n]x n +T 2 = 

[33>; 3 + +[3n]x n +T s = 

H .... 

[nn]x n +T,, = . . . (12), 

where the first equation may contain all the dependent variables ; the second does 
not contain x x ; the third does not contain x x and x 2 ; and so on, the last containing 
only one dependent variable, say x n . A diagonal system is characterised by the order of 
the variables in the diagonal, and there are as many diagonal systems as there are linear 
permutations of x v . . . ., x n . We shall see presently that the coefficients [11], [22], 
. . . \nn\ are determined to a constant factor when the " diagonal order " of the 
variable is given. We shall speak of them as the diagonal coefficients. We shall now 
shew that 

Every determinate system of linear equations with constant coefficients can be 
reduced to an equivalent diagonal system in which the dependent variables have any 
assigned diagonal order. 

In the first place, we prove that 

From any two equations 

U 1 =(ll)a; 1 +(12>: 2 + .... +(lrc>i„+S 1 = . . . (13) 
U 2 =(21> 1 +(22>c 2 + .... +(2?iK+S 2 = . . . (14) 

we can always deduce an equivalent pair, one of ivhich does not contain any assigned 
dependent variable, say x v 

For the equations 

LU! + MUj = (15) 

L'l^ + M'U^O (16) 

where L, M, L', M' are any integral functions of D with constant coefficients, will be 
equivalent to (13) and (14), provided the modulus of (15) and (16) with respect to (13) 
and (14) be constant — that is, provided 

LM'-L'M = const (17). 

Now, if g be the G.C.M. with respect to D of (11) and (21) ; so that 

(ll)= r/ (ll)' , (21W21)', 



SYSTEMS OF ORDINARY LINEAR DIFFERENTIAL EQUATIONS. 169 

where (11)' and (21)' are integral functions of D, which are prime with respect to D, and 
we take 

L=(2iy , M=-(iiy, 

then, by a well-known theorem (see my Algebra, vol. i. chap. vi. § 11) we can always 
determine two integral functions of D, L' and M', such that 

(21)M'+(11)L' = const. 

If L, M, L', M' be thus determined, the coefficient of x 1 in (15) will vanish, and the con- 
dition (17) will be satisfied. Hence our first preparatory theorem is established. 

We next prove that 

A determinate system of linear equations iviih constant coefficients can always be 

replaced by an equivalent system in which any given variable, say x 1} occurs in only one 

of the equations. 

Let the system be 

^=(11)^+ +(lttK+S 1 = .... (18) 

U n =(nl)x 1 + +(nn)x n +S n = Q . 

If any of the equations already do not contain x x , set them aside and consider those 
that do contain x 1} say the first r. By our last theorem, we can replace U], = 0, U 2 = 
by an equivalent pair, U/ = 0, U 2 ' = 0, one at least of which does not contain x x . Set 
that equation, say U/ = 0, aside along with the others that do not contain x x . If U 2 ' = 
happens not to contain x 1} set it aside also : if not, take it along with the remaining 
r - 2 equations. We thus have a system of r—l equations, with which we can deal as 
before. By continuing this process we shall finally arrive at a single equation which 
must contain x x , since the original system is determinate. This last equation, conjoined 
with the n — 1 equations set aside in the above process, constitute a system equivalent 
to (18), only one equation in which contains x v 

The possibility of reducing any given system (18) to a diagonal system is now obvious. 
We arrange the dependent variables in any order, say x 1} x 2 , x s , . . . . , x n ; then deduce 
from (18) an equivalent system only one equation, say the first, of which contains x v 
The remaining n—\ equations form a determinate system for x. 2 , x s , . . . . , x n . From 
this last deduce an equivalent system the first equation of which alone contains x 2 ; and 
so on. We thus arrive finally at a diagonal system, such as (12). 



Properties of a Diagonal System. 

It is immediately obvious that the determinant of a diagonal system reduces to the 
product of the diagonal coefficients. Hence by the second form of our equivalence 
theorem it follows that 

The product of the diagonal coefficients of any diagonal system is, to a constant 



170 PROFESSOR CHRYSTAL ON THE EQUIVALENCE OF 

factor, equal to the determinant of any system to which it is equivalent ; or, in our 

notation, 

|(11)(22) (nn) \ =[1.1] [22] [nn] . . . (19). 

Every diagonal system may be solved by meant; of a seines of linear differential 
equations with constant coefficients each involving only a single dependent variable. 
For we have merely to solve the last equation of (12) to get the complete value of x n ; 
then, x n being known, the second-last will give the complete value of x tl _ x ; and so on. It 
will be observed that all the arbitrary constants in the expression for x n (o) n in number, 
where co n is the degree in D of the coefficient [nn] ) are introduced at once. In finding 
x n _i we introduce <o a _ x fresh arbitrary constants, where w w _x is the degree in D of \_n — 1, 
n,— I]. These w n _ x arbitrary constants are the arbitrary constants which occur in the 
expression for x n _ x , but not in the expression for x n . In addition to these, x n . x may 
contain all or some of the arbitrary constants already introduced into the expression 
for a ■ ,. 

Next, we find x n _ 2 by means of a differential equation of degree, <u n _ 2 , x n _. 2 will 
therefore contain o) n _ 2 uew arbitrary constants, together with all or some of those intro- 
duced into x n _ x and x„. And so on. 

The whole number of arbitrary constants introduced, none of them superfluous, in 
the complete solution of the system is o) l + oi. 2 + . . . . +<o a , that is the degree in D of 

[11] [22] [nn]. Hence from (19) we have a rigorous proof of the general 

theorem referred to in the beginning of this communication, viz. : — 

The order of any determinate system of ordinary linear differential equations with 
constant coefficients is equal to the degree in D of its characteristic determinant. It is 
obvious that the equivcdence of a diagonal system is not affected by adding to any 
equation U,. = of the system any linear combination L / ._ 1 U,._i+ . . +L, l U, l = (ivhere 
L,._!, &c, core integral functions of D with constant coefficients) of all the equations that 
follow it. For the diagonal coefficient of the resulting equation U,. + L,. _ 1 U,._ 1 + . . + 
L;|U„ = remains unaltered, and it alone appears in [11] . . . . . [nn], the determinant 
of the system. Advantage of this may be taken to simplify calculations in the practical 
solution of a diagonal system. Into the question as to the maximum of simplification 
thus attainable I shall not enter ; but it appears from the above remark that the 
coefficients of a diagonal system, other than the diagonal coefficients, are not uniquely 
determined when the diagonal order of the dependent variables is assigned. 

It is easy, however, to show that the diagonal coefficient of any variable is deter- 
mined when the aggregate of the variables that follow it in the diagonal order is given. 

For let x,. be the variable in question, x,._ x , x,._ 2 , , x n those that follow it in any 

given order, and let the corresponding diagonal coefficients be [rr], [r— 1, r— l], , 

[n, n] : and let the corresponding coefficient in the case where x,. again stands first, but 
.'",_i, x,._ 2 , . . . , x n are arranged in any other order be [rr]', [r— 1, r—lj, .... [nnj. 
Since the last r equations form by themselves in the two cases a pair of equivalent 
determinate systems for x,. t x,._ h , x„, we must have 



SYSTEMS OF ORDINARY LINEAR DIFFERENTIAL EQUATIONS. 171 

[rr][r-l,r-l] [nn] = [rr]'[r-l, r-lj [nn]' . , (20) 

by the second equivalence theorem. Again, the last r — 1 equations in the two cases 
form a pair of equivalent determinate systems for cc,._ l5 x r _ 2 , , x n ; hence 

[r-l,r— 1] [?m] = [r-l, r-1] [nn]' . . (21). 

Now, from (20) and (21) we have [VrJ^JV, r]', which proves our theorem. 

It is obvious, alike from considerations already detailed regarding the successive 
introduction of the arbitrary constants, and from the possible derivations by means of 
which we can deduce from a given diagonal system an equivalent one with a different 
diagonal order of the variables, that the diagonal coefficient for any given variable is 
of least degree in D when it is first, and of greatest degree when it is last in the 
diagonal order; and that promotion in the diagonal order' may increase but cannot 
diminish the degree of the diagonal coefficient. 

The diagonal coefficients in the two extreme cases are of greatest importance ; because 
the degree of the diagonal coefficient, when the variable is last in the diagonal order, is 
the whole number of arbitrary constants in the complete expression for the dependent 
variable in question ; and the degree, when it is first, in the number of arbitrary constants 
which occur in the expression for that variable and do not occur in the expression for 
any of the others. We are thus led to investigate rules for calculating the first 
and last of the diagonal coefficients for any given order of the dependent variables, say 



£,.-■■,& ! &', • • • 



Ki ,...., Kn 



fc» 



f l > • • • • j Kji 



be the systems of multipliers of (12) 'with respect to (18), and of (18) with respect to 
(12), where, since the systems are equivalent, all the multipliers must be integral 
functions of D. Then we have, inter alia, 

[11] £'=(11), [11] 9l '=(21), , [11] Kl ' = (nl) . . . (22) 

<11)£ + (21)&+. . .+(nl)& = [ll] .... (23) 

From (22) it follows that [11] must be a common divisor of (11), (21), , (nl) ; 

and from (23) that the G.C.M. of (11), (21), , (nl) must divide [11] exactly. 

Hence [11] must, to a constant factor, be simply the G.C.M. of (11), (21), , (nl), 

!h say. 

Again, the complete system for determining k x , , /c„ is 

(11) Ki + (21)k 2 + . . .+(nlV„ = 

[ . . . . (24). 

(l,n-l) Kl +(2,R-l) K . 2 + . . . +(n,n-l) Kn =0 ' 

(ln) Kl + (2n)K 2 + . . . +(nn)K n = [nn] 

VOL. XXXVIII. PART I. (NO. 2). 



172 

1 f therefore 



PROFESSOR CHRYSTAL ON THE EQUIVALENCE OF 



{11} {22} {nn} | 



(25) 



denote the reciprocal matrix to | (11) (22) (nn) |, we have from the first n-\ 

equations of (24) 

k x :ko: :Kn={ln}':{2n}': . . . .{nn}', 

wliere {1^'j {nn}' are the set of relatively prime integral functions of D which 

arise by dividing {in} {nn} by their G.C.M., G n say. Therefore 

K 1 = X{ln}', /c 2 = \{2«-}', , K n = \{nn}', 

wliere X is some integral function of D, or a constant. 

Now, since | i;^ K n \ must be constant, (12) and (18) being equivalent, it 

follows that X must be a constant ; for | ^ x n 2 K n | obviously contains the factor 

X. We must therefore have 

[nn] = \[(ln){lnY+(2n){2nY+. . . +(nn){nn}'] = \ \ (11)(22) . . . nn\/G n . (26), 

that is to say, we must have, to a constant factor, [nn] = K/G jl5 where K is the char- 
acteristic determinant of the original system. 

We are thus led to the following general rule : — 

Form the schemes 



u 2 
u„ 



(11) (12) (In) 

(21) (22) (2n) 

(ril) (n2) (nn) 



(27), 



and 



<J\ 9-2 
1 9 



(Jn 



{11} {12} {In} 

{21} {22} {nn} 

{nl} {n2\ {nn} 



(28), 



G l (x 2 G„ 



by means of the matrix of the given system and its reciprocal matrix, g l , g 2 , , g nl 

«ncZG 1 ,G 2 , , G n being the G.C.M.s of the constituents of the respective columns, 

then 

!J\ > 9l i ' On j 

K/G x , K/G 2 ,....., K/G ;l 



(29) 



are the diagonal coefficients of the variables x^ , x. 2 , , x n when these are first 

and last in diagonal order respectively. 



SYSTEMS OF ORDINARY LINEAR DIFFERENTIAL EQUATIONS. 173 

And, further, the differential equations for determining the variables separately are 
(since V„ = KjUj + . . . + K„U„) 



(30). 



g; 1 ' G, ! ' G x 2T ^ G 1 



\ 



7=r «8»+ p — Si + 'p — S. 2 + + -p — S K — 

/vi o^Aer ivords, these are the last equations in diagonal systems when x l , x n 

are last in diagonal order respectively. 

It must be noticed, however, that (30), considered as a system, is not equivalent to 
the given system, although it gives correctly each of the variables separately — that is to 
bay, it gives correctly a value for each variable which, along with a corresponding set of 
properly- determined values, will constitute a solution of the system. 

Conditions for the "Simplicity" of a Diagonal System. — Prime Systems. 

When a diagonal system contains only one differential equation, this equation must, 
of course, be the last (unless it be possible to select from among the dependent variables 
a set of r which can be determined wholly by non-differential equations, each of which 
will therefore contain no arbitrary constant whatever in its expression, a case which we 
may suppose excluded ; see Example 1, p. 175). In this case the order of the system is 
the order of this last differential equation. All the diagonal coefficients [11], [22], 

, [n— 1, n— 1] reduce to constants, for no one can vanish in a determinate 

system ; and the first n — 1 equations are non-differential equations, by means of which 
we can calculate successively the variables in terms of those previously found, and of 
their differential coefficients. Such a system may be called a Simple Diagonal System. 

There are two important criteria for the possibility of reducing a given system to a 
simple diagonal system. 

Since in all cases we have 

K = [nri] [u-1, n-l] [22] [11], 

and since the operations by which [11], , [mi] are derived from the coefficients 

of the original system are all rational, it follows that the coefficients of all these integral 
functions of D are rational functions of the coefficients of the original system. It follows 
that, if K be irreducible in the sense that it has no integral factors whose coefficients are 
integral functions of the coefficients in the operator-coefficients in the original system, 

then all the functions [11], , \_nn~] , except one (under ordinary circumstances 

the last), must reduce to constants, and this one will then differ by a constant factor 
merely from K. Hence the following important theorem : — 

If K be irreducible, then every equivalent diagonal system to ivhich a given system 



174 PROFESSOR CHRYSTAL ON THE EQUIVALENCE OF 

can be reduced is simple. In such a ease, each of the dependent variables will involve all 
the m arbitrary constants required by the order of the system. 

Again, if in the reciprocal matrix there be any one column, say the last, which is 
relatively prime, then, if we take the variable x n corresponding to that column as the last 
in an equivalent diagonal system, the last equation in that system will, by (30), be 
Ka"„ + , &c, = — that is to say, [nri] will differ from K merely by a constant factor ; and 
therefore [11], , [n — 1, n — 1] must all reduce to constants. Hence 

For every 'prime column in the reciprocal matrix of a given system a series of 
equivalent simple diagonal systems can be formed in ivhich the corresponding variable 
is the last variable. 

In particular, if every column of the reciprocal matrix be prime, then every equivalent 
diagonal system will be simple, and the expression for each of the dependent variables 
will contain all the arbitrary constants of the system. 

This second criterion obviously includes the first ; for, if K be irreducible, all the 
columns of the reciprocal matrix must be prime. 

By a preliminary transformation ive can always make the solution of any system 
depend on the solution of another system cdl the columns of whose characteristic 
determinant are prime. Such a system we may call a prime system. We have merely 
to introduce new variables X ] , , X„ such that 

g 1 x 1 =X 1 , , . . . .g^'x n =X„ (31). 

Having solved the new system in X l5 , X„ , we pass to the solution of the 

original system by solving system (31), which consists merely of single equations for the' 
separate variables. 

A prime system is by no means necessarily transformable into a simple diagonal 
system ; it has, however, the characteristic property that, in every equivalent diagonal 
system, the first equation is non-differential. 

Practical Methods of Solution. 

The foregoing theory suggests various methods for solving linear systems with 
constant coefficients. The most natural method, and, if a particular solution of the 
system cannot readily be guessed, possibly the best, is to transform the system into 
a prime system, and then reduce the latter to an equivalent diagonal system, simplify 
this last as much as possible, solve it, and then pass back to the original system. 

We may also proceed step by step, as follows : — Transform to a prime system, 
separate one of the variables, say x v in this system by reducing it to an equivalent 
system in which x x occurs in only one equation. The rest of this new system is a 
determinate system for x. 2 , . . . . , x n . Transform this last to a prime system, then 
separate one of the variables as before, and so on. 



SYSTEMS OF ORDINARY LINEAR DIFFERENTIAL EQUATIONS. 175 

When the .system has a prime reciprocal matrix, and therefore admits of being 
transformed into a simple diagonal system, the ordinary method of determining the 
arbitrary constants by substitution is convenient. This method may be employed in 
any case, and the work can be shortened by ascertaining from (30) what terms actually 
do occur in the complementary functions of the respective variables. 

Other modifications suggest themselves in the light of the foregoing theory ; but it 
seems unnecessary to pursue the matter here. Nor shall I enter into the interesting 
question as to how far the general principles above laid down could be extended to 
systems of ordinary linear equations whose coefficients are not constant. 

But it may be useful to append some simple examples to illustrate some of the points 
of the general theory. 

Example 1 : — 

(D*+l) ^-f(D 2 + D + l) y = t, 
Bx+ (D+l)y=e*. 

The characteristic determinant of the system reduces to 1 : we should therefore expect 
that the solution contains no arbitrary constants at all. In effect, if we use the 
multiplier-system, 

|1,-D I 

I D,-D--l|' 

whose determinant is constant, we deduce the equivalent system 

-y=i-2e', 

whence x = 1 + 1 - 3e\ y = 2e ( - 1. 

The fact that a system of differential equations may have a general solution which 
involves no arbitrary constant whatever, is suggested naturally enough both by the 
foregoing theory and also by Cauchy's theory of the order of any system. It lias, 
however, been so seldom emphasised that it seemed worth while to give the present 
simple instance of the phenomenon in question. 



Example 2 



Here 



(_3D 2 -4D + 1),+(D 3 + 3D 2 + 5D- l)y = 0f ' ' W " 



K 



D J -L> + 2, 2D-2 
-3D 2 -4D + 1, D 3 +3D 2 +5P-1 
S D(D+1) 3 (D 2 +1). 

The reciprocal matrix — viz., 

I'D 3 +3D 3 + 5D-1, 3D- + 4D-1 
I -2D + 2, D 3 -D + 2 



17(5 



PROFESSOR CHKYSTAL ON THE EQUIVALENCE OF 



has all its columns prime ; hence any equivalent diagonal system must be simple. If we 
take x as the last variable, the matrix of the system of multipliers will be 

L, M, 

D 8 +3D 2 +5D-1, _2D + 2 ' 

where L and M must be so determined that 

L(21 ) - 2) + M(D 3 + 3D 8 + 5D - 1) = const. 

The quickest method in practice for determining L and M will be understood from 
the following special application : — Let 



fc- = D 3 +3D 3 +5D-l 



Eliminating D 3 , we get 



(0). 
(7). 

(S). 



1)^-2/ = -8D 2 -10D + 2 

Next, eliminating D 2 by means of (/3) and (8), 

(I)- + 4D)^f-2/-= -18D + 2 (e). 

Finally, eliminating D by means of (/3) and (e), 

(D*+4D + 9)u-2v= -1G; 

we may therefore take L = D 2 + 4D + 9 and M = -2, so that the required multiplier- 
matrix is 

D- + 4D + 9, -2 

D 3 +3D 2 +5D-1, -2D + 2 

This reduces the system (a) to 

-1G?/ + (1) 5 + 4D 4 + 8D 3 +4D 2 + 7D + 16>; = 6«- 
D(D + l) 3 (D 2 +l)r = -4c-'; 
n simple system as predicted. 

From this we get by the familiar methods, 

x=A+(B + Ct+Et 2 )e- t + ¥ cost+Gcsmt+^fe-' , 
and, substituting this value in the first equation, 

y = A+H(2B + 3C-3E)+(2C+6E)*+2E* 2 }e-' 

+ F ( ., )S / + Q sin t+ 1(- 1 - 6^ + Qt*+ tfy- 1 . 

Lte+Py+(D-1>=0, 
(D-l)x+V*y+(D-l) 2 z=0 } 
(D + l)x+ Jf'v + (I )" - 1 >- = 



Example 3: — 



SYSTEMS OF ORDINARY LINEAR DIFFERENTIAL EQUATIONS. 

If we put rj = D/y , £= (D — \)z, we reduce (a) to the prime system 

T)x +v + £ =0 

(D-1)»+D,+(D-1){=0;; 

(D + 1>+D 2 ,,+(D + 1)£=0 



177 



08); 



for which 



K= D ,1,1 

D-l, D, D-l 

D + l, D 2 , D + l 
-D(D-1)(D 2 -2D-1) 
= -D(D-l)(D-a)(D-/3), 



y). 



where a = 1 + J2 , £ = 1 - V 2 
The reciprocal matrix is 



-D 3 +2D 2 + D, o , D 3 -2D 2 -D 

D 2 -D-l , D 2 -l j -D 3 + D+l 

-1 , -D 2 +2D-1, D 2 - D +1 



(S), 



the columns of which are prime, except that corresponding to 77, which contains the 
factor D — 1. 

The system (/3) is of the fourth order, and the forms in the complementary function 
are 1, e\ e at , e 131 , the second of which does not occur in 77, owing to the presence of the 
factor D — 1 in the corresponding column of (S). Hence the solution lias the form — 

r = a + b et+c <:M +d efi, 
n =f +9 c at +h d 31 , 
f = /•+/ c' + i» e at +nept} 

in which the four constants a, b, c, d may be taken as the four arbitrary constants of the 
system (/3). 

By substituting the separate parts in (ft), we find at once 

/=«, k=-a, l=-b, g=2c, h = 2d, m=-(3+ >/2)c, n=-{3- J2)c, 

In the present case, since the particular integral isx , = 0,^ = 0,{=0, this, which is 
merely a simplification of the ordinary method, is practically the quickest method of 
solution. 

In order, however, to illustrate the general theory given above, we may give the 
reduction to a diagonal system. 

Using the multiplier- system, 

D-l, - 1 I 
D.-l I ' 

we can replace the first two equations of (/3) by two others, one not containing £, and 
thus derive 



178 



SYSTKMS OF ORDINARY LINEAR DIFFERENTIAL EQUATIONS. 



(D 2 -2D + 1).»- , =0 
(D s - D + l)r>+0,,+f=0 



! 



By means of the multiplier-system, 



D + l, - 1 
D, - 1 



for the last two equations of (e), we derive 






Finally, using 



(D 8 -2D+1)oj- n = 
(D s -B)x -D 2 , ; = 

(D 3 - P 2 - 1) x - D'-'t? - f = 



I) 2 , - 1 
D 2 + l, - 1 



on the first two equations of (£), we deduce the diagonal system 

( r)3_D 2 -i),-DW=o, 

(D , -? 1 D 3 +2D ! -D+l)x- ip ) 
(D'-3D ;i +D 2 + D).r =0, 



which, by using the last equation in the second, may be reduced to 

1 



(D 3 -D 2 -l)ar-D 2 ^-^=0 
(P*-2D + l)x- l} =0 
(D 4 - 3 D 3 + D 2 + D) x = ) 



(e). 



(D- 



(v). 



The system (17) may now be solved very readily, and leads to the same result as 
before. 

After solving (/3) by either method, we pass back to (a) by solving the two equations 

Dy=,,.CD-l)a=f; 

and thus get the complete solution of (a) involving six arbitrary constants. 



( 179 ) 



III. — On Bird and Beast in Ancient Symbolism. By Professor D'Arcy 

Wentworth Thompson, Jr. 

(Read 4th June 1894.) 

I 

The following essay, except for one or two slight corrections and additions which 
I have since interpolated, was read before the Eoyal Society of Edinburgh in June 
1894. Very shortly thereafter, M. Jean Svoronos published in the Bulletin de 
Correspondance HelMnique (Janv.-Juillet, 1894) a learned pa.per " Sur la signification 
des types monetaires des anciens," in which he demonstrated with an elaborate 
wealth of illustration the astronomic significance of many coin-types, the precise 
point that the greater part of this essay of mine was written to prove. Beginning 
with coins on which a beast- or bird-emblem is figured together with the symbol of 
a star, and passing on to others where the star-symbol is omitted, M. Svoronos 
shows clearly that in a very varied series of coin-types, the Lion, the Bull, 
the Eagle, the Horse, and so forth, represent not merely these creatures themselves, 
but their stellar namesakes : in short, that, in more or less obscure and occult 
shapes, astronomic emblems are imprinted on a vast range of ancient coins, 
just as in open and acknowledged forms they are visible, for instance, on the 
coins of Antoninus Pius. So clearly is all this put forward by M. Svoronos that 
my paper might well have remained unpublished were it not that I think I take 
the case somewhat further than he does. For, whereas M. Svoronos is content to 
demonstrate the symbols of individual constellations, I have attempted also in certain 
cases to show that the associated emblems correspond to the positions relative to 
one another of the heavenly bodies, in some cases to the configuration of the sky 
at critical periods of the year or at the festival seasons of the cities to which the 
coins belong. In some other respects, also, I have attempted to carry to a further 
issue the general considerations suggested by the astronomic hypothesis. 

In a Glossary of Greek Birds now passing through the press, I have indicated, so far 
as the scope of the work and the size of the book permit me, certain astronomical 
phenomena which seem to me to be veiled or symbolised in art and in literature 
in connection with certain bird-names. The present essay deals with the same 
hypothesis in greater detail, and adduces a somewhat different set of illustrations in 
support of it. 

VOL. XXXVIII. PART I. (NO. 3). 2 A 



1^0 



PROFESSOR D'ARCY WENT WORTH THOMPSON ON 



In Miss J. E. Harrison's book on The Mythology of Ancient Athens there is to be 
found a learned, but, to my thinking, a mistaken explanation of the great relief of 
Cybele in the Hermitage Museum at St Petersburg. This monument seems to me to be 
capable of a far simpler and far more interesting explanation. The two annular symbols 
on either side of the central figure are not, to my mind, mere adjuncts of the picture, 
(f>[a\ai, or votive gifts offered to the goddess; they are the ancient symbols of the sun, 
as we still find them to this day in astronomical and astrological works. The figure 







Fig. 1. — Cybele Relief (Hermitage Museum, St Petersburg)/ 



to the right of the group, with the water-jar on his shoulder, is no mere 71-^000-71-0X0? or 
temple-server, but the Water-bearer himself; nor is the Lion "a mere lap-dog," or 
symbol of the dominion of the goddess. The group represents, in short, the Sun in Leo 
and the Sun in Aquarius. 

The statement that this great monument displays two zodiacal signs would scarcely 
deserve credence, and the fact, if admitted, would be of comparatively small interest, 

* I am indebted for the loan of this engraving to Messrs Macmillan & Co., and for that of the Lion and Bull on 
p. 182 to Mr John Murray ; the other engravings are all the gift and handiwork of Mrs W. R. H. Valentine, Dundee. 



BIRD AND BEAST IN ANCIENT SYMBOLISM. 181 

could we not show that these two signs were in some way related to one another, 
and had a definite meaning in their conjunction. Now, in the first place, Leo and 
Aquarius are just six signs or six months apart ; and, in the second place, they 
were, in the epoch immediately preceding that of classical astronomy, the tropical or 
solstitial signs. The sun, which had its summer and winter solstices in Cancer 
and Capricorn in classical times, stood in Leo and Aquarius at the corresponding 
seasons in the immediately preceding age ; and just as we still speak of the tropics 
of Cancer and Capricorn, though the sun in its precessional course has now moved into 
Gemini and Sagittarius, so the yet older signs of Leo and Aquarius held their place 
in Hellenic speech and symbol when Cancer and Capricorn had superseded them in 
scientific astronomy and in actual fact. In a word, the monument was emblematic of 
the midsummer solstice, when the sun was rising in Leo and Aquarius was setting in the 
west ; and the heavenly signs are shown circling round the head of the Earth-Mother. 

While this is the simplest explanation, and the one which first occurred to me of 
the conjunction of the two signs, there is yet another very closely akin, which I offer 
as a perhaps preferable alternative. When the sun is in Leo, that is to say (at the 
epoch of which I speak) in the month of the summer solstice, the full moon of 
that month is situated in the opposite sign of Aquarius ; and it is therefore 
conceivable, and even probable, that the monument represents the sun and moon in 
opposition at midsummer, that is to say, the season of the full moon in the month of Leo. 

Whichever of these two closely allied interpretations of the monument we prefer, we 
should, in either case, expect to find the same subject repeated in other monuments 
and works of art, were it a type so ancient and so important as I take it to be. 
On the very next preceding page of Miss Harrison's book we find it again : the Lion 
sits at Cybele's feet on the left, and on the right we see the Watering-pot and 
hand of Aquarius, whose retreating figure has been broken away. In another of Miss 
Harrison's figures we have one-half of the same subject, the Lion lying in Cybele's lap, 
symbolising equally well the midsummer season. And yet again, we meet with the 
whole group in a certain very ancient Mithraic monument. 

The frieze sculptured along the base of the St Petersburg monument is eminently 
corroborative of my hypothesis. It represents the ancient and widespread device of the 
Bull and Lion in combat, the Bull kneeling with lowered head to the left, the Lion on 
the right in attitude of attack. In the same epoch when Leo and Aquarius occupied 
the place of the solstices, the Bull marked the spring equinox, the ancient opening of 
the year: — " Candidus auratis aperit cum eornubus annum Taurus." 

The Bull and the Lion, then, if we follow the same line of argument as we have 
taken in regard to the major group, represent spring and summer, spring giving way 
before the heats of summer ; or, restricting ourselves to the face of the sky as revealed 
at one particular date or moment, we may interpret the victorious Lion as Leo standing 
in mid-heaven precisely when Taurus is setting in the west. 

The conjunction of the Bull and Lion is extraordinarily frequent in art, and their combat 



1M> 



PROFESSOR D'ARCY WENTWORTH THOMPSON ON 



is an ancient simile in literature. It is hard, indeed, to believe that these allusions and 
representations refer to actual combat of the two animals, or to depredations on the part 
of the lion upon the peasant's kine. The allusion is far more subtle and more mystical. 
Pace Herodotus, it is hard to believe that there is the smallest proof of the existence of 
lions in Greece within historic times : the bull would, in any circumstances, be an animal 
seldom attacked by the lion ; it would never be found near the haunts of the lion in 
Africa, and probably not very often in Assyria ; and the conventional picture of the 
combat is stereotyped and unnatural. The stories of the Eagle attacking the Bull are 
scarcely more untrue to nature, and are equally mystical in their interpretation. 

The following sketch, taken from a shield found at Amathus in Cyprus (Cesnola, 
Cyprus, pi. xx.), where certainly lions never occurred, represents the conventional picture, 
which we find repeated over and over again. The Bull is to the left of the Lion ; its 




Fig. 2. — Lion and Bull in Combat, from a Cyprian Shield. 



attitude is that of the constellation Taurus, and we note in particular its bent knee as 
Aratus describes it (Phaen. 517) : — 

Ta vpov Se (TKeXewv oacrtj -TrepicbaiveTai o/cAa£, 

or in Cicero's translation : — " Atque genu flexo Taurus connititur ingens." 

If we pass to the great and much-neglected store of ancient symbolism in coins and 
gems, we find the same subject again and again. And here, though it is not my 
purpose in this short essay to deal fully in argument with other views, I must make one 
brief digression. Professor Ridgeway's now widely accepted views on the patterns of 
ancient coinage would, as it seems to me, give a meaning to coin-types where numismatists 
had none to offer before, but it is a meaning foreign to all we know of ancient symbolism. 
His theory that not merely the ox, but the tortoise, the fish, the silphium plant, the ear 
of corn, and so forth, represent articles of general or local commerce whose barter the 
coins replaced, is to give to the nations of antiquity a numismatique boutiquiere, which 
might be paralleled in modern times were the people of Gushetneuk to stamp a red 



BIRD AND BEAST IN ANCIENT SYMBOLISM. 183 

herring on their groats. Mr Bidgeway's theory is of a piece with the speculations of 
those who, running folk-lore to the death, seek to read antiquity in the light of savagery ; 
who see the childhood of the world in a culminating age of astronomic science, symbolic 
art, and mystical religion, and who arrive at what I unhesitatingly regard as miscon- 
ception by the double blunder of unduly depreciating the complexity of initial or archaic 
Greek thought, and unduly exalting the importance and too freely correlating the 
results of their own study of incipient or semibarbarous civilisations. We must see 
fallacy in any theory which treats as nascent and primitive the civilisation of a period 
of exalted poetry, the offspring of ages of antecedent culture ; which sees but a small 
advance on recent barbarism in ways of life simple in some respects but rich in 
developed art and stored with refined tradition ; that looks only for the ways and habits 
and thoughts of primitive man in races supported by a background of philosophical 
and scientific culture of an unfathomed, and maybe unfathomable, antiquity. Behind 
early Hellenic civilisation was all the wisdom of Egypt and the East, and the first 
Greeks of whom we have knowledge looked upon the old Heaven and the old Earth not 
with the half-open, wondering eyes of wakening intelligence, but with perceptions trained 
in an ancient inheritance of accumulated learning. 

On gold coins of Croesus we find our two symbols of the Lion and the Bull, some- 
times facing one another, sometimes joined by their necks. Whatever may be precisely 
signified in the latter case, it seems to me plain enough that the collocation of 
the two animals here, together with the presence of the Lion alone, 
or of the Lion with other animals, on coins of the same place and 
period, should make us hesitate to see in this Ox-type the emblem 
and memento of a primitive trade : apart even from the inherent 
improbability involved in supposing that the Ox was the great 
staple of commerce and fixed standard of value over mainland and 
islands, through regions inland and maritime, among people peaceful Fig. 3.— Coinof 
or warlike, stationary or nomadic, pastoral or mercantile ; while any 
argument that, in this particular case, we had the old trade-symbol of the Ox coupled 
with the Lion as a personal or dynastic crest is negatived by the frequency and wide 
distribution of the same two figures in conjunction. 

If the Lion and the Bull in combat represent zodiacal signs, we should expect them to 
do so in like manner when figured separately or when associated with other symbols. 
Numismatists have long recognised the Lion on coins of Leontini, Syracuse, Apollonia 
on the Euxine, &c, as a solar symbol* : it is evidently in relation to the sign Leo that 
it is so ; and I need scarcely remind the reader that the same sign is, in fable, the Lion 
of Nemea, with whose defeat the solar Hercules began the cycle of his labours.t 

* Of. Head, Hist. Numorum, pp. 131, 152, 236, &c. 

t Cf. Dupuis, Origine de tons Us cultes, i. p. 191, &c. From this learned and original work, oftener quoted, as 
Crkdzer says (Symb., iv. p. 696), than acknowledged, I have got great help, not in the inception but in the elaboration 
of my theory. 




184 



PROFESSOR D ARCY WENTWORTH THOMPSON ON 



Let us defer for the present the consideration of planetary signs in conjunction with 
zodiacal ones, but let us pause to consider a few more representations of the zodiacal emblems 
when displayed alone. In perusing a series of figures of coins or gems, we often meet with 
the same animal in duplicate, forming a pair of symmetrical and identical but opposed 
figures ; and the pair of figures, or in some cases three placed triradially, are sometimes 
set in a figure of revolution. It seems to me that I find such figures mainly in con- 
nection with the tropical or solstitial signs, and sometimes also with the equinoctial 
ones. Taking the former case, we have to deal with the ancient tropics of Leo and 
Aquarius and the later ones of Cancer and Capricorn ; while our corresponding equi- 
noctial signs are, more anciently, Taurus and Scorpio, and in the later epoch Aries and 
Libra or, as an equivalent to the latter, the Chelae of the Scorpion. Of these, the Crab, 
the Balance or its substitute the Claws are in themselves marked by a bilateral 
symmetry so conspicuous that we need not seek for further reduplication. In the case 
of Aquarius I have not found such a symmetrical reduplication, unless the bilateral form 
of the two-handled Jar be in itself its equivalent. But in all the other cases I find it. 




Fig. 4. — Coin of Amphipolis. 




Fig. 5.— Coin of Delphi. 




Fig. 6. — Archaic Gem 
(I. B. and K., pi. xix. 1). 



An archaic bracelet, reproduced and familiarised by Castellani, consists of a split 
ring, whose two ends are fashioned into the semblance of Rams' heads ; the whole 
ornament is, to my thinking, a symbol of the year, from Aries to Aries. We have 
a similar notion expressed in the annexed figures of the two Goats or in the 
corresponding one of the two Rams ; these I take to be emblematic of the dividing 
line of the solstice or equinox, as the succeeding figure illustrates the pivot-point of 
the equinox in Taurus, with the Moon in conjunction. And turning from glyptic 
or numismatic to monumental art, we think at once of the twin Lions guarding 
their central column on the Lion-gate at Mycense : that column I take to be the 
Lion-guarded pillar of the solstice ; I fancy it was once crowned with a solar globe ; 
and I furthermore venture to prophecy that that temple-gate will be found in some 
manner oriented to the midsummer sun, as is the great avenue of our own astronomical 
temple of Stonehenge. 

From a study of the Lion and the Bull we are led, somewhat unexpectedly, to a 
consideration of the Pleiades. This notable constellation occupies a remarkable position : 
it is set in the sign of the Bull, and very nearly at the intersection of the ancient 
equator and the ecliptic. In astronomical descriptions the place of the constellation 



BIRD AND BEAST IN ANCIENT SYMBOLISM. 



185 



varies somewhat in relation to the imaginary and variable figure of the Bull. 
Hipparchus set it near the Bull's thigh, but it is more usually and more anciently 
placed, as by Aratus, on the Bull's back. In many languages the Pleiades are mixed 
up with the names or images of birds. Besides the well-known and ancient belief that 
■n-XeidSes was originally 7re\eidSes, we have the fact that the Chinese still picture the 
constellation as a bird, and the existence of the old English name "the Hen and 
Chickens," to which correspond the French Poussiniere, the Pillalou codi of the 
Indians, the Succoth Benoth of the Hebrews, and many similar names. Add to these 
the names of the individual stars themselves, or so many of them as we can understand. 
The first Pleiad is ' ' AXkvovvj, the Halcyon, and the second is MepoTt}, which is connected 
not only with fiepo^b but with the remarkable word nepov-n-as, which Mr Bent found 
used in Syra in the Cyclades to mean simply a bird, opvis. I think from all these 
analogies I am justified in taking the bird figured on the Bull's back in coins of 
Eretria, Thurium, &c, and on Egyptian representations of the Sacred Bull, to be nothing 
more nor less than the associated constellation of the Pleiades. 





Fig. 7. — Archaic Gem, probably Parthian. 
(Imhoof-Blvmier and Keller, pi. xxi. 
14). 



Fig. 8. — Tetrarlrarhm of Eretria. 



Not to be dissevered from this connection is the story of the Dove of the Argonauts, 
which Hew between the clashing rocks in the passage of the Hellespont. Was not 
that BoWojooc a transit through the Heavenly Bull, and is it going too far into the 
regions of hazard to see in the Sym-Plegades a name (corrupt by popular misunder- 
standing) akin to Plejades ? 

In considering the relative positions, at critical periods, of the Sun and the Pleiades, 
we seem to light on an explanation of the great myth of the Halcyon's Nest. On the 
day of the winter solstice, mid-winter's day, the Pleiades occupied at sun-set the mid- 
point of the heavens : — 

vb^ /ULUKp)] koi X € ^f JLa l JL ^ (r> l v ^ ^ 7r ' n\eui<5a Svvet, 

' The Pleiad is in mid-heaven as the long(est) winter night sets in." It was precisely 
at this period that the Halcyon was said to lay her egg, when the turning sun rose to 
renovate the year. What is the meaning of the line following that which I have 
just quoted : — 

vv£ /uaKprj Kai ^eijua /mecrtjv <T exJ IlXeidoa ouvei, 
k ay u> -rap irpodvpois velaao/uai vofievos, 



186 PROFESSOR D'ARCY WENTWORTH THOMPSON ON 

" I stand in the door- way dripping from my bath." That is what the Sun says 
as he emerges from Oceanus. 

A consideration of the account given in Aristotle (H.A., bk. v. 8, 542 b) and 
of the citations made there from Simonides, compel us to interpret the phenomenon as 
astronomical : 

>'] cT dXicviov TiKTei irepl Tpo7ra$ toc? j(eifxeptvd<i, 8io kcu kuXovvtcu orav evSieivcu yevowTcu at 
rpoirai, dXKVovlSes q/mepcu, kirTO. fxev irpo Tpoirwv, e7rra Se fxeTu. Tpoirds, KaOdirep kcu ^ifxcovlSiji; 
eTTOirjcrev, '12? ottotolv ^ei/uepiov kcito. fiijva -iriv\)<JKr\ Zev$ %/u.a.Ta TecraapcucaloeKa, XaOavefAov tc 
fj.iv wpav KaXiovcriv eTnj(dduioi, lepdv TrcuSoTpd(pov TroiKiXag uXkvovos. Tivovtcu <?' evSieival, otuv 
av/u8>] votiov$ yiveaQai t«? Tpoirds, Ttjs TlXeidSo? fiopelov -yeyo/xeV^?. 

We may render the last lines of this passage as follows : — " And the fine weather is 
to be met with when the sun turns in his southern tropic, and when at the same time 
the Pleiades are found in their highest (northern) elevation." # 

The Pleiades had also an intimate relation with the season of spring. In the ancient 
epoch of which we speak, when Taurus was the equinoctial sign, the sun rose associated 
with the Pleiades at the Vernal Equinox, in what was the opening of the ancient year ; 
for this reason the Pleiades were the stars of spring, the Vergilise of the Latins. And 
the Halcyon is the same as the 

d\nrup(popos elapos opvis, 

a verse which admits, syllable for syllable, of literal translation, not merely " the sea- 
blue bird of March," but " the bird of spring that brings up the sun from the sea." 

M. Svoronos has pointed out that the numismatic emblem of a bunch of grapes is to 
be looked upon as another representation of the constellation of the Pleiad. An Homeric 
Scholiastt tells us that BoVjou? was actually a name given to that constellation ; and 
M. Svoronos figures a very remarkable coin of Mallos in Cilicia, where doves are 
represented whose bodies are formed of bunches of grapes, the dove-emblem and the 
grape-emblem of the Pleiad being here united or intermixed. The case is a very 
interesting one, because it seems to give an example not only of the influence of foreign 
symbolism, but of the direct influence of loan-words from foreign sources. I take the 
grape-symbol to be due to a substitution of the notion of olvog for oiW?, a rare pigeon- 
name ; and the latter to be nothing more than the Semitic njV, Ionah, a dove. 

Having started our discussion with the Lord of Beasts, let us glance at the symbolic 
attributes of the King of Birds ; but of these symbolic attributes, which are innumer- 
able, we may be content with a very brief discussion. The Eagle is depicted in Greek Art 
and Literature as hostile to various creatures, of which the chief and the most frequently 
mentioned are the Swan and the Hare. I find nothing of zoological significance in these 
relations, The eagle does not prey upon swans ; and though it may catch here and there 
a leveret, the hare is certainly not one of its main objects of attack. 

* For further remarks on this obscure and difficult myth, see my Glossary of Greek Birds, pp. 31, 32. 
t Schol. II., xviii. 480 ; Ideler, Sternnamen, p. 317. 




BIRD AND BEAST IN ANCIENT SYMBOLISM. 187 

Eeading the statements in the light of astronomical symbolism, we are at once 
struck by the following circumstances. The constellation Aquila is adjacent to the 
constellation Cygnus ; the former rises immediately after and as it were in pursuit of 
the latter, but the Swan, lying further to the north, has a longer course to make above 
the horizon, and accordingly is still visible for a while after 
Aquila has set. Aristotle tells us, in a passage of hitherto 
unquestioned zoological import, that the Eagle attacks the 
Swan, but is in turn defeated by it. I can find no zoological 
truth in the statement, but the astronomical coincidences 
here related accurately correspond to it. As regards the 
Hare, we note that the constellation Lepus is on the eastern 
horizon when Aquila is precisely on the western. Not far 
from Aquila stands the constellation Vultur; and Aquila 
and Vultur are frequently associated together, both by Fig. 9.— Decadrachm of 

Agrigentum. 

classical writers and by the Arabs, as Aquila or Vultur 

cadens and volans, or yty /cafl^ei/o? and -7rer6ixevo<s, nesr-el-waki and nesr-el-tair, 
whence our modern names Vega and Altair applied to their two principal stars. 
These, then, are the two eagles that devour the Hare on the famous decadrachm of 
Agrigentum and in the great simile of the Agamemnon, olwvwv fia<ri\evg fiaaihevcri vewv. 
a KeXaivos, o t e^oiriv apyas, . . . fiocrKO/Aevoi \aylvav. 

It remains to be seen whether we can discover any reason for these particular 
phenomena of the heavens attracting particular attention and being especially selected 
for representation. The Hare rises, and the Eagle, pursued by the Swan, sets just as 
Cancer has risen. The Crab is in like manner a frequent subject on coins, and in some 
very beautiful coins of the same city of Agrigentum we have the Crab on one side and 
the Eagle on the other. The whole symbolism probably, therefore, has reference to the 
tropic of Cancer, and to the midsummer rising of the sun in that sign in the classical 
epoch as in the older days it was at the same season of the year associated with Leo. 

The multitudinous numismatic representations of the Dolphin (on coins inland as- 
well as maritime) provide us with a severe test of the validity of the astronomic 
hypothesis. The constellation of the Dolphin set very nearly as the Lion, the Hydra, 
the Hare, and the Dog-star rose ; it is associated with the Lion on coins of Syracuse, 
Tarentum, Velia, and Nacona, with the Serpent on coins of Priansus, Motya and 
Messene, with the Hare on those of Messene, and with the Dog on those of Phocaea. # 
With the circumstance that it stood directly opposite to the Lion, setting as the 
latter rose, we may correlate its title of King of Fishes under which it ruled side by side 
with the King of Beasts, reigning over Oceanus while the Lion was Lord of the visible 
sky. It stood, with Capricorn, in mid-heaven at the rising of Aries, and is associated 
with the Goat and Ram on coins of Delphi and with the former animal on those of 
Paros. It rose as Argo and Gemini set, and is figured with a ship on coins of Megara 

* As well as on a gem figured by Imhoof-Blumer and Keller, pi. xx. fig. 18. 
VOL. XXXVIII. PART I. (NO. 3). 2 B 



188 PROFESSOR D'ARCY WENTWORTH THOMPSON ON 

and with the Dioscuri on coins of Tarentum. It rose with Sagittarius, and together 
with it on coins of Tarentum we have Taras (?) armed with a bow and arrow. In its 
place in the heavens it is closely encircled by Pegasus, Cygnus and Aquila ; the Eagle 
is found with it on coins of Messene, Istrus, Motya and Sinope, and the Swan on 
those of Argolis ; while Pegasus is associated with it on coins of Corinth, and is 
probably also to be understood in the Horse of Rhaucus and the Horse and Rider of 
Tarentum. 

The statement in Aristotle (H. A. vi. 12, 566b) that the Dolphin disappears for a 

month in summer, crvix^alvei §e kcu acpavl^ecrOai olvtov virb Kvva irepi TpiaicovO' rj/xepa^ (regard- 
ing which statement Aubert and Wimmer naively say, " iiber diese Verhaltnisse scheinen 
aus neuer Zeit gar keine Beobachtungen zu existiren ") is simply an astronomical fact 
concerning the constellation, interpolated into a passage in the main zoological. It was 
probably the same constellation under another guise that Apollo had to overcome ere 
he mounted to the sky : Ae\<plvr]v S' eSd/aaa-aev, kou alOepa valev 'AttoXXwv, Nonn. Dionys., 
xiii. 28. And, passing over a hundred fables all bearing kindred astronomic reference, let 
me cite one more circumstance in point. We are told by Pausanias (vi. 20, 7) that a 
brazen Eagle and Dolphin guarded the acpea-ig at Olympia * ; and when we bear in mind 
that in the heavens Aquila and Delphinus stand opposite to Leo, does it not seem fit 
and proper that the Eagle and Dolphin should mark the end of the Olympian chariot- 
course, where the fabled Slayer of the Lion laid down the mimic race-course of the Sun ? 
The Owl on Athenian coinage is an emblem of great interest, but involved in not a 
little difficulty. Svoronos takes it, with some hesitation, to correspond to the constel- 
lation simply known as "Opn? ; but that " bird "-constellation is, in all cases that I am 
acquainted with, identical with Cygnus the Swan. Although the Owl on Athenian 
coins is sometimes associated with a lunar crescent, I am, for my part, inclined to look 
upon it as itself a lunar emblem. We may call to mind, in support of this view, the 
Euripidean fragment, 

And remembering that Athene in Homer is always nocturnal, and is even definitely 
stated by Porphyry {Euseb., Pr. JEv. iii. 11) to have been a Moon-Goddess, we find not 
a little to support the hypothesis. In the light of this conjecture, the common 
association of the Owl with an Amphora on Athenian coins becomes interesting ; for it 
may be that the Amphora is the symbol of Aquarius, and the relation of Aquarius to the 
Moon has been discussed already. t When Athene in the Iliad appears in the shape of a 

* As also in the Circus Maximus at Rome ; cf. Juv. vi. 590, Dion. Cass. xlix. 43. 

t The study of what I take to be the lunar symbolism of the exclusively silver coinage of Attica, and other 
considerations of a like nature, have led me to the discovery of a singular and suggestive coincidence. We are told by 
Herodotus (iii. 89) that the values of gold and silver in ancient currency stood to one another in the ratio of 13 : 1 ; 
but Mommsen (Hist. Mon. Rom., ed. Blacas, i. p. 407 ; cf. Head, Hist. Numorum, p. xxxv.) and others have shown 
that this statement is only approximately correct, and that the true ratio was 133 : 1. There is no evidence that 
there were the same fluctuations between the relative values of the two metals which are now so common (Head, I.e.). 
Two problems are here presented to us for solution : first, How was this ratio kept steady and unchanged during many 



BIRD AND BEAST IN ANCIENT SYMBOLISM. 189 

swallow, there again the lunar crescent of the swallow's wings is at once suggested to 
me ; and the similitude to the swallow of Ulysses' bow is of the same nature : no 
twittering swallow's note was ever like to the twang of the great bow, but the bow 
was bent like the crescent wings of the bird, j(e\iS6n eliceXt] avryv. 

To draw yet another illustration from the mystical Kingdom of Birds, what was the 
pitiful lay of dSwvqis, a<W'?, a»/<W?, or d^vv, that fills line upon line of Attic chorus and 
Dorian and Ionian hymn with obtrusive melancholy ? Was it not simply the old dirge 
of Adonis, the Dead March of the year, the keening song over the grave of the 
Sun, whom the sorrowing East bewailed when women wept for Tammuz ? "Was it 
not merely a disciple of another sect who said he preferred the swan's song to the 
nio-hting-ale's ? 

Whether this or some other be the true explanation of the legend of the nightingale's 
song, it is quite plain from the frequent hints of many writers that some esoteric 
meaning was associated with the songs of Halcyon, Nightingale and Swan. Ltjcian, for 
instance, gives us such a hint and a very notable one, though even he only points, with 
sealed lips, to the immemorial riddle whose solution he cannot or must not tell : ovk av 
eyoifxev elireiv fiefSalw? out ' AXkvovoov Trepi, out ' ArjSovwv /cAe'o? ^e avOoov, oiov irapeSocrav 
TraTepes, toiovto ko.1 7rai<r\v e/moh, w opvi Opi'ivaov pteXwSe, 7rapaSw<jw tu>v o~wv u/ulvwv irepi, /ecu gov 
top evuefiTj teal (pi\avc)pov epooTO. 7roX\dias v/j.vww. — LlJCIAN, Hcdc. 

In a certain small number of coins and gems the representation of astronomic 
phenomena is set forth in clear and concrete fashion, with no riddle of esoteric 
symbolism. The annexed figure of a gem (from Asia Minor) represents in this obvious 
way the constellations of the Dragon and the two Bears : 

Maxirnus hie flexu simioso elabitur Anguis 

Circum perque duas in morem fluminis Arctos. — Virg., G., i. 244. 

centuries of antiquity ; and, second, how or why was it chosen and established in the first instance ? Now, it seems 
to me more than a mere coincidence that 133 : 1 :: 365 : 27*4, the last number being precisely the period in days of 
the Moon's revolution round the earth. In short, the ratio of gold to silver, established and maintained, I fancy, by 
astronomic science and astrological superstition, was simply and precisely the ratio of the solar year to the lunar 
month, the natural relation of the metal of the Sun to the metal of the Moon. 

If this speculation be justified, it may further throw some light on the use of electrum as a standard of currency. 
This metal was an alloy of gold and silver in the proportion of 73 to 27 ; and it has been pointed out by Hultsch that 
its value according to this scale would be to silver as 10 to 1, when gold was to silver as 13"3 to 1 : — that is to say, 
gold : electrum : silver :: 13*3 : 10 : 1. It is generally assumed by numismatists that electrum was a native alloy, 
coined for convenience to avoid the trouble of separating the silver from the gold. This explanation is in my opinion 
altogether inadequate. The very fact that the ancients knew accurately the composition of the alloy is enough to 
indicate that the separation of the two metals presented no serious difficulties to them : moreover, I do not believe 
that an alloy of so precise a composition ever existed in large quantity or widely distributed : and, lastly, though some 
sueh alloy undoubtedly did exist native, we are twice told by Pliny (R. N. ix. 65, xxxiii. 23) that it was made or 
imitated artificially. It seems probable to me that electrum was an alloy ingeniously devised and skilfully manufac- 
tured to form a new standard in simple decimal relation with silver, to take the place of the old, complex and 

10 13'3 

inconvenient astronomical standard of gold. And the ingenious framing of a -y in place of a -y- ratio and standard 

would form a parallel case to the splendid adaptation by which the Babylonians divided the circle into 360 degrees, 
thus, by a sbght and simple change, co-ordinating with a sexagesimal notation, the old 365 or 365J degrees into which 
the Chinese still divide the circle, as the Sun divides the circle of the year. 



190 



PROFESSOR D'ARCY WENTWORTH THOMPSON ON 




Fig 10.— Draco and the Two 
Bears on an Asiatic Gem. 



Imhoof-Blumer and Keller, from whose Thierbilder I have borrowed the figure, 
simply state that these three constellations are represented ; but they do not state, and 
perhaps did not perceive, that there is a deeper astronomic interest in this gem, to wit, 

that as nearly as may be its centre coincides with the North 
Pole of the heavens in the epoch of classical Greece. The 
pole, which now lies in the Little Bear, then stood in Draco 
between the Two Bears, somewhat nearer to the little one ; 
and the Two Bears are the Miltonian " Star of Arcady and 
Tyrian Cynosure," 

Magna minorque ferae, quarum regis altera Graias, 
Altera Sidonias, utraque sicca, rates. — Ovid, TV., iv. 3, 1, 

The whole gem is an exquisite picture of the polar region of the sky, precisely as Aratus 
describes it in a famous passage copied over and over again by Latin poets : — 

Kai ij.iv Treipaivovtri Svoo 7roXoi dju.cpOTe'pwOev' 

dXX' o-fiev ovk e7ri07TTO?, b o avnoq e/c (Sopeao 

v\]/66ev wiceavoio' Svu) Se fiiv d/xcpig e'-^ovcrai 

* A.QKTOI afxa Too-vowa-i (to St] KaXeovrai ' A./j.a£ai). 

al S' ?jTOi KecpaXdg /xev eir ipva? atev e^ovaiv 

dXXtjXwv, atel Se KaTMjudSiai (popeovrat, 

e/JuraXiv eig ojyUOt/? TeTpafxpievai .... 

Kai tiiv fxev i\.vv6<Tovpav eir'iKXr)<jiv KaXeovaiv, 

Ttjv S' krepr\v 'J&XiKrjv. 'EXtVj; ye /mev avSpeg 'A^aiol 

etv dXi TeKjualpovrai "iva -^py vrjas ayivelv 

Trj S' dpa Qoivitces tt'ktvvoi Tvepoaxri QaXacrcrav. 

aXX' i] fxev KaQapri /ecu eTrKppaacraaQai eroifit] 

7ro\Xr/ (paivo/mevr) 'EXiKtj trpwTrjs euro vvkto$' 

rj o eTeprj oXiyrj fxev, ciTap vavTricriv dipeiwv 

fietoTep)] yup -Kucra TrepicrTpe(peTai trrpocpaXiyyr 

Trj kui ^EiSovioi lOvvrara vavTiXXovrai. 

rug Se Si' dfjKpOTepas o'lrj TroTa/moio uiroppw^ 

eiXeirai /xeya Oavjua, ApaKWv, irep'i t afxipi t eayias 

luvpios' at S' apa ol cnreiptjs eKarepOe (pepovrat 

"ApicTOi, Kvaveov iveepvXayfxevai wKeavolo. — ARAT., Ph., 25—48. 

And now, to close my story, the conclusion that I wish, in a general way, to draw is, 
that to understand the solemn and sacred and cherished myths of antiquity, we must 
seek an interpretation in their ancient source in an ancient heaven. The one science 
that the civilised races of old loved and understood was astronomy. 



* Cf. Virg., G., i. 244 (supra cit.) ; Ovid, Met, iii. 44 ; Id., F., iii. 107 ; Lucan, iii. 219, viii. 173, ix. 539 ; Sil. 
Ital., Pun., iii. 192, 665, xiv. 456 ; Val. Fl., i. 17, v. 69, vi. 40, &c. 



BIRD AND BEAST IN ANCIENT SYMBOLISM. 191 

" Their Wise Men 
Were strong in that old magic that can trace 
The wandering of the stars." 

The Herald in the Agamemnon was not a solitary watcher of the skies, nor did Wise 
Men in the East monopolise the adoration of the stars ; but generations of Hellenic 
priests, like their fathers and their brethren in Egypt and Chaldea, had regarded the 
strength of Mazzaroth and the bands of Orion and the sweet influences of Pleiades. 

These guardians of an esoteric knowledge divulged their store little by little, in myth 
and allegory, in the sacred art of sculptor and of poet, and through the mystified lips of 
the teller of tales and the singer of songs. The traditional belief that Perseus and Bootes, 
Cepheus and Heracles, were earthly heroes translated to a restful seat in the stellar firma- 
ment, is an inversion of the true order of things. The Heroes that were set in the sky had 
been drawn thence in the beginning : the Gorgon's head was not the creation of a poet's 
fancy nor the legend of an antique chronicler, before a place was found for it in the star 
Algol ; but patient study and accurate knowledge of the Demon Star, with its mysterious 
flashes and its rhythmical wax and wane, preceded the allegorical conception of Medusa's 
snaky head. 

Let us, then, forsaking traditional acceptations, admit that the Chiruasra must be 
carried at once to the land of Chimseras ; that Perseus and his Gorgon's head must not 
be taken to Lycia, nor Amalthsea and the two Bears to Crete, but that all of them must 
be raised to the sky. In all these cases earthly geography must be left aside. The 
Bull, the Crab, the Goat, and the Ram on silver drachma and golden daric must not be 
regarded as articles of trade, but must be placed in the zodiacal ring. The voyage in 
quest of the Golden Fleece was not through the Dardanelles, towards Colchis or the 
Caucasus. No dove out of a dove-cot was set free between the clashing Symplegades. 
Further, if to these zoological illustrations we add the number of the Achaean chiefs at 
Troy or of the champions on either side at the epic siege of Thebes : if we couple Helen, 
Queen-Goddess of beauty (the moon-faced beauty of the East), with her twin stellar 
brethren : if we think of the Phseacian King, whose sailors sailed from his far western 
island to eastern Eubcea, saw there, on the triple judgment-seat, Rhadamanthus or Ra 
Amenti and his brother-kings of the under-world, and returned in one day home 
again, we catch more than a glimpse of that stellar symbolism which veiled from 
vulgar eyes, even perhaps from the eyes of the tellers of the story, a splendid vista of 
priestly lore. 

The stellar symbolism that I here advocate is, I maintain, a different thing from the sun- 
myths, dawn-myths, and so forth, which are now to a large extent deservedly repudiated. 
We cannot ascribe to the civilised nations of antiquity the puerile conceptions of nature 
that are congruent with a stage of awakening intelligence and with the crude results of 
untrained observation. Rather are we dealing with the elaborated gain of ages of 
scientific knowledge, with the thoughts of a people whose very temples were oriented 
to particular stars or to critical points in the journey of the sun ; whose representations 



192 BIRD AND BEAST IN ANCIENT SYMBOLISM. 

of Art, on frieze and pediment, in tragedy and epic, were governed by what would at 
first appear to be a tyrannical convention : which convention, however, so far from 
hampering their genius, seems, under the influence of a wholesome restraint, to have 
moulded their art into more beautiful, more poetic, and more sanctified forms. 

And we may stay a moment to remember that it is not only Art but Custom 
also that was fettered by conventionality and sanctified by religion. At Olympia, 
in the beginning of each Leap-year cycle, the noblest youth of Greece raced, round 
the symbolic pillars, their horses emblematic of the Horses of the Sun ; thereby 
glorifying a God whom they thus ignorantly worshipped. Even so. we read in the 
second Book of Kings how their Phoenician cousins worshipped with like ceremony 
the same God. And all the while, in the evening and the morning, priests and 
irpocnroXoi watched, measured, and compared the rising and setting of Sun and Stars, 
in temples that were astronomical observatories, to the glory of a religion whoso 
mystery was astronomic science. 

This dominant priesthood, whose domain was knowledge, holding the keys of 
treasured learning opened the lock with chary hand, and veiled plain speech in fantastic 
allegory. In such allegory Egyptian priests spoke to Greek travellers who came to 
them as Dervish-pilgrims or Wandelnde Studenten. It was this Sybilline knowledge; 
that an iEschylus, an Ovid, or a Virgil, Master of Wizards, here and there half revealed. 
It is this dragon-guarded treasure of secret wisdom that we may yet seek to interpret, 
from graven emblem, from symbolic monument, from the orientation of temple- walls ; 
from the difficult interpretation of non-Hellenic names, of hero and heroine, of Solar 
God and Lunar Goddess, of mysterious monster and fabled bird, of celestial river and 
starry hill : names that were first written in the ancient and learned language of a people 
wiser and more ancient than the Greeks. 



( 193 ) 



IV. — Two Glens and the Agency of Glaciation. By His Grace 
The Duke of Argyll, K.G., K.T. (With a Map.) 

(Read 1st April 1895.) 

The group of questions which are connected with the Glacial Age seem to me to be 
among the most interesting and the most difficult in the whole science of geology. 
They include the question of Time — since, perhaps, the only hope we have of even reach- 
ing any unit of time in geological changes lies in the phenomena of the Glacial Age # 
The question of the comparative slowness or suddenness of great physical changes is not 
less directly involved. Bound up with this again is the question of the sudden or slow 
destruction of the extinct forms of life, and the introduction of new forms to replace 
them. The connection between Cosmical and Terrestrial causes of change comes directly 
into our view, and then the nature and operation of the terrestrial forces which were 
brought into play. I am very sceptical as to many of the solutions which have been 
proposed for most of these questions, and still more for the theories which profess to 
answer them as a whole. There is nothing to be done but to accumulate evidence in 
detail — to observe facts well, that is, completely — and avoid looking only at such of them 
as tell in favour of some preconceived hypothesis. 

It is one of the great delights of the physical sciences that the questions they concern 
are inexhaustible. I do not mean only that each one of those questions always leads on 
to some other. I mean that even each question in itself is always turning up in some 
new light, or new aspect, even when we may have been long familiar with the phenomena 
which suggests it. The truth is that the very fact of such familiarity is perpetually the 
cause of some fresh departure, because it extinguishes that sense of surprise, and puts 
even that natural curiosity to sleep, out of which all intelligent questioning of Nature 
comes. Things which we see every day are precisely those which are most apt to conceal 
their lessons from us — and it is only, perhaps, some accidental suggestion that awakes us 
to obvious interpretations which we had never thought of before. Such, I confess, is 
the experience I have lately had concerning a question in geology which I have long- 
regarded as of the highest scientific interest. I refer to the physical agency, and the 
physical conditions under which what is known as the glaciation of our West Highlands 
was effected. The science of geology presents no more perplexing problem. Living, as 
I do, in a country where the marks of glaciation are abundant, but at the same time far 
from universal over the whole surface, I have long come to the conclusion that one agency 
widely believed in cannot possibly have been the producing cause. It cannot have been 
what is called an Ice Sheet, or an Ice Cap, or ice in any form, under whatever name it is 

VOL. XXXVIII. PART I. (NO. 4). 2 C 



194 HIS GRACE THE DUKE OF ARGYLL, K.G., K.T., ON 

called, which moved upon, and moved over all the hills, in enormous masses, and there- 
fore with an enormous pressure universally applied. The marks appear to me to be 
incompatible with any such supposition. They are essentially partial, local, and what 
may be called selective. We cannot attribute this partiality to the disturbing effects of 
subsequent obliteration ; because the same rock in the same place which is highly glaciated 
on some one part of its surface is wholly untouched upon other parts. Some rock 
surfaces, indeed, do exist, which have been evidently wholly covered by, and ground 
down under enormous and continuous moving pressure into one smoothed and polished 
Moor or dome, and these rocks are of the greatest interest in showing to us what 
the characteristic effects of such an agency must always be. But though they exist, they 
are comparatively rare. For every one specimen of this kind of glaciation there are 
hundreds of thousands in which the smoothing, abrading, or scratching agency has acted 
on some one side of a rocky surface and has left the other side rough and untouched. 
There is, however, one general rule or law which can be clearly traced. The direction 
from which the agency came, and the direction towards which it moved, is almost always 
determined by the existing configuration of the land, — that is to say, rocks on the sea- 
shore have been smoothed by some body which must have moved along the coast from 
the higher hills towards the lower ranges, or towards the outlets of the arms of the sea 
on which they are abundant. In like manner, in the glens not occupied by water, they 
follow the lines of the glen from its head towards its opening. So far, this is easily 
intelligible, because, if the configuration of the country was substantially what it is now, 
ice moving in the form of ordinary glaciers, such as those of Switzerland, would, and 
must, be guided in their course by the direction of the hollows in which they lie, or, if 
moving in the form of floating or floe-ice, would equally be guided by currents similarly 
determined. But there is this difference to be noted, that even small glaciers, such 
as those which we now have on the Alps, do produce surfaces wholly polished upon those 
particular rocks over which they actually move in a solid mass. Very partial glaciation, 
therefore, such as leaves large parts of a rock wholly untouched, cannot indicate the 
passage of ice in this particular form, whilst it is not only consistent with, but character- 
istic of ice floating in water, and made by currents to impinge upon rocks which interrupt 
its passage. The floating masses grate along the shores, or the rocks which constitute a 
shore for the time being — catching the projecting surfaces as they pass, and necessarily 
leaving untouched the retired or sheltered surfaces, which do not obstruct the way. 
Then there is one phenomenon, which clearly indicates the same agency — although under 
the same conditions, which startle us not a little — and that is the glaciation of rock 
surfaces which constitute the summits of high hills, far above the general level of the 
whole country, and not situated in any glen or hollow which could possibly have guided 
either a solid glacier or a mere shore current. These glaciated tops are often smoothed 
or striated on one surface only — with a sheltered side as rough and as well-marked as any 
similar rock upon the existing shores. This is quite inconsistent with the passage of 
that enormous kind of glacier which is denoted under the name of an Ice Sheet or an Ice 



TWO GLENS AND THE AGENCY OF GLACIATION. 195 

Cap. Such a body could not have failed, by its vast pressure, to have ground down all 
the surfaces on which it rested, or over which it passed ; and the appearances actually 
presented are generally quite distinctive of an agency much lighter and more passing 
in its work. The same lesson is taught by another phenomenon very common on 
our hills ; and that is the position of enormous boulders and masses of rock left poised 
or "perched" upon the very tops of ridges, isolated hills, in such a manner that no 
conceivable agency but that of floating ice-floes could have placed them and left them 
where we now see them. Nor are these blocks deposited only on the tops of conspicuous 
hills, but also on knolls and elevations of every sort and kind, just as would naturally 
happen on shoals and banks in a rising or falling sea. Moreover, it is to be observed that 
many of these stones are not rounded, as they must have been if they had been rolled 
under water, or dragged along in the lower layers of a moving glacier. Many of them 
are rough, and even angular in a high degree — just as they might have fallen from some 
overhanging cliff, or have been torn off by the splitting power of frost. These are all 
arguments to show that even if an ice sheet had ever existed as a moving mass, it could 
not have produced the phenomena which we actually see. But besides these arguments, 
there are others which condemn the supposed ice sheet as a physical impossibility — 
inasmuch as no adequate cause of motion has ever been made out for such an assumed 
" flow " of such ice-masses. 

Putting all these considerations together, I had long; come to the conclusion that our 
glaciation has been effected mainly by ice-floes and occasional icebergs in a glacial sea, 
which rose at least some 2000 feet above the level of our present ocean, and in which 
powerful currents were running in a general direction from N.E. to S.W. There is a 
natural and legitimate aversion to such an explanation. It defies altogether that 
impression of the stability of the relative position and levels of sea and land, which is one 
of the strongest preconceptions we derive from our own uniform experience. Forgetting 
how very short that experience is, and how inadequate to justify any conclusions as to an 
unknown past, our preconception is farther helped by the extreme difficulty of even 
imagining any physical cause for a submergence of the land, which would seem to have 
been so recent and so passing. These are excellent reasons for reserve and caution in our 
reasoning, but they are no excuses for reluctance in admitting the evidence of obvious 
facts, or for carelessness in making closer and closer observation as to facts which may 
not be equally apparent at first sight. After all, we must remember that geology has 
made us familiar with the idea of the interchangeability of sea and land, almost 
everywhere over the globe, as one of its most certain facts ; and the assumptions, so often 
tacitly made, that all those changes must have been always infinitesimally slow, are 
assumptions in the highest degree precarious, and founded on theories for which there is 
really no adequate foundation. We must remember also that the movements which arc- 
suggested, although they startle us by their evident recency in point of time, and by our 
conception of their magnitude in elevation and depression, are, after all, movements of 
infinitesimal smallness when considered with reference to the size of the globe, and with 



196 HIS GRACE THE DUKE OF ARGYLL, K.G., K.T., ON 

reference to such forces as we know to have worked, and to be still working in its interior. 
A movement of elevation or of depression in any part of our terrestrial surface, to 
the extent of 2000 feet, would be quite invisible to a spectator standing at the distance 
of a few hundred miles, and might easily be produced by the operation of such causes as 
we see must have been concerned in a thousand cases of geological change. In this, as 
in all other cases of reasoning on physical phenomena of this class, what we have to look 
for, above all things, is not merely simple effects, which may plausibly be accounted for 
by invoking some one supposed cause ; but for those complicated and complementary 
effects which, in great variety and number, are sure to accompany the operation of such 
great physical forces as those which we may invoke. The evidence which we should seek 
is essentially cumulative — full of incidental and subsidiary testimony arising out of a 
thousand facts, which, at first sight, may not seem to have any bearing upon each other, 
or upon any common explanation. And this is precisely the kind of evidence which only 
comes to us gradually — as the result of long and continuous observation illuminated by 
equally continuous thought. Suggestions, indeed, may arise in our minds quite suddenly, 
and may be of such a character as to be of the highest value, throwing a flood of light on 
conclusions which had before seemed to rest on a basis hardly adequate to support them, 
but which now seem very largely confirmed if not actually established. 

A suggestion of this kind has lately occurred to me in respect to the agent of glaciation 
in the Inveraray district, from certain facts with which I had, indeed, been long familiar, 
but which I had never before put together in connection with this particular problem. 
This suggestion it is my object in the present paper to explain. 

The parish of Inveraray occupies some ten or eleven miles of the north-western shore 
of Locli Fyne, and reaches to within three or four miles of the extreme end or head 
of that long and very deep arm of the sea. The large fresh-water lake of Loch Awe lies 
in another deep depression, which, roughly speaking, lies parallel to this upper reach of 
Loch Fyne ; and the two sheets of water are separated from each other by a range of hills 
from six to seven miles across from shore to shore " as the crow flies." The trend of Loch 
Fyne is in that general direction of N.E. and S.W. which is so conspicuous a feature 
in the physical geography of the West Highlands. The parish is deeply trenched by two 
great leading glens which join the main valley of Loch Fyne at an acute angle — running 
pretty nearly north and south, but with some deviation towards the prevalent N.E. and 
S.W. These two glens, named respectively Glenaray and Glenshira, are nearly parallel, 
separated by a range of hills and moors hardly exceeding two miles in breadth. This 
range terminates abruptly in the curious conical hill of Duniquoich, which rises immedi- 
ately above the town and castle of Inveraray. As the whole country is occupied by one 
great geological formation, these two glens, which traverse it in such close proximity to 
each other, might well be expected to present a close resemblance. It is true, indeed, 
I hat the rucks of the district have a certain variety, which is quite competent to produce 
in close proximity considerable varieties of aspect. They consist of the whole series 
comprehended in the general name of the Mica Schists, together with great masses of 



TWO GLENS AND THE AGENCY OF GLACIATION. 197 

intrusive material, these for the most part being a porphyritic granite. As the Mica 
Schists include not merely beds of mica slate but beds also of quartzite and of limestone 
and of a material which has been suspected to be stratified volcanic ash, there is ample 
room for the agencies of denudation to do a good deal of differential work — quite capable 
of accounting for many different aspects of the surface. Moreover, as the sedimentary 
beds are all more or less inclined at a high angle, glens cutting through them are liable to 
have sides or walls, some of which present the slope, and others the escarpment sides of 
the strata, according to the direction in which these are traversed. But if due attention 
be paid to those causes of a certain amount of difference in the scenery, we can easily 
separate them from other causes which have operated in other ways. In the case of these 
two glens there are some special differences which are very striking. The separating wall 
of mountain is common, of course, to both glens, and the two other, containing ridges to 
the west and east respectively, rise to about the same elevation, and consist very much 
of a repetition of the same, or closely similar beds. Yet, in spite of their close structural 
resemblance, the two glens present a violent and curious contrast to each other. The 
mountain slopes on either side are as steep in the one glen as in the other. But in Glen- 
shira they are comparatively smooth and regular in surface, showing the slopes and 
escarpments on either side clearly, and unencumbered by rough knolls or lower ranges of 
hill. The bed or bottom of the glen is still more remarkable in the same way. It is a 
smooth and level valley, occupied by a rich alluvial soil, and running about four miles 
from the sea before its river reaches the elevation of 100 feet. Its placid, peaceful, and 
rich pastoral character is very beautiful — but singularly unlike most other highland glens, 
and reminding us more of the glens and valleys in Westmoreland. Glenaray, on the 
contrary, on the other side of the same dividing ridge, is in every respect different — it 
is a typical highland glen, occupied by a rapid brawling river, which plunges over 
three successive waterfalls and runs the rest of its course down a bed encumbered with 
stones and rocks. The whole surface of the glen partakes of the same rough and 
irregular aspect. Along the lower slopes near the river, it is encumbered with enormous 
quantities of loose stones of every size and shape — some of them of gigantic proportions, 
and most of them quite unworn and unrounded, — presenting, on the contrary, many sharp 
angular surfaces. Farther up the glen its floor is largely occupied by great conical 
mounds of clay, sand and gravel, with a multitude of included stones. They represent 
typically the boulder clay. Through many of these the line of the public road to 
Dalmally, on Loch Awe, has been cut — showing sections which prove that these mounds 
have generally not even a nucleus of solid rock, but are composed entirely of transported 
materials from the grinding down of the rocks around. The included stones are strongly 
smoothed and striated — very fine specimens of polishing and striation being common in 
the sections. In short, the whole course of Glenaray is a conspicuous example of the 
most characteristic glacial action — of a very marked and violent kind. One side of it — 
the eastern side — presents a surface of moor full of knolls and mounds all covered with 
loose transported stones, and rocks of every size and shape. The escarpment to the 



IDS HIS GRACE THE DUKE OF ARGYLL, K.G., K.T., ON 

west, which is extremely steep — much of it almost precipitous — is, however, free, or 
almost free, from similar appearances — as if the agency, whatever it may have been, 
had been deflected to the eastern side, and had scoured out the faces opposite. 

Here, then, we have a whole series of contrasted conditions in two closely contiguous 
glens, which suggest some curious questions. How can we account for the almost 
complete exemption of the one glen from glacial work, when that work is so evident and 
so predominant in the other ? What is there in the physical configuration, or in the 
geographical position of the one as compared with the other, which can be rationally 
connected with this great difference ? The moment we ask this question, if we are fully 
awake to its significance, there is at least one negative answer which is certain. No 
cause operating over the whole area of the country can possibly be the agency which 
has thus discriminated so immensely between these two glens. This conclusion seems 
absolutely to exclude the agency of some universal " ice-sheet " higher than all the 
mountains, and " flowing " from some gigantic confluent glacier-mass which moved from 
the German Ocean over the whole Western Highlands. Yet this has been the dream of 
man)' writers of the extreme glacial school. Any such agency must, in this particular 
case, be put out of count — quite apart from the many physical objections which lie 
against it as applicable anywhere or at any time. 

But there is another agency much less theoretical, and much more probable, as 
applicable to similar phenomena elsewhere — and that is the action of comparatively 
small local glaciers formed upon the containing hills of all our deeper glens, and taking 
the usual and natural course of such bodies down the slopes, and passing down the 
valleys into which they fall. If there has ever been any glacial age at all in Scotland, 
and if the mountains which we now see were ever at any time during that age above the 
surface of the sea, and exposed to the usual atmospheric conditions of an arctic climate, 
the snow must have gathered and consolidated on all the higher elevations into true 
glacier ice, and small local glaciers must have been formed upon them — just as they are 
now formed on the higher hills in Norway and elsewhere in Northern Europe and 
America. That such glaciers must have existed in the Highlands, during the glacial age, 
is practically certain, and there are abundant evidences of their action in many of our 
glens. But the curious thing in respect to the cases of Glenaray and Glenshira is that it is 
impossible to account for the difference between them by supposing that a local glacier had 
existed in Glenaray and none in Glenshira. This impossibility lies in the fact that, of the 
two glens, the mountain ranges which fall into the unglaciated Glenshira are far higher, 
and far more certain to have gathered glacial snows, than those which fall into the highly- 
glaciated Glenaray. It is true that the more immediate containing walls of both glens 
arc very nearly of the same altitude. But in the case of Glenaray, these nearer ridges 
and summits lead to no contiguous mountains beyond which are still more elevated, but, 
on the contrary, fall off at once on every side — towards Loch Fyne, in one direction, and 
to Loch Awe upon the other. On the other hand, the containing walls of Glenshira, at 
i;- head, do lead up to contiguous mountain surfaces of much higher elevation, and 



TWO GLENS AND THE AGENCY OF GLACTATION. 199 

especially to the peaks, conies, and precipices of Ben Buie, which rises to the height of 
3100 feet. If local glaciers had been formed anywhere in the whole district, they must 
have been formed on the tops and flanks of this mountain — and they must have moved 
down Glenshira if they had acted as all such bodies do elsewhere. Two very deep and long- 
ravines, each of them draining large surfaces of mountainous slopes and moors, fall into the 
head of Glenshira : and it is quite impossible that, if local glaciers were ever formed in 
Glenaray, they should not have been also formed, and in much greater volume, at the top 
of Glenshira. There is, indeed, no comparison between the extent and elevation of the 
gathering ground at the head of Glenshira and the comparatively trifling area capable of 
serving the same purpose in the case of Glenaray. The conclusion is inevitable that the 
agency which seems to have been present in great force in Glenaray, and to have been 
cither wholly absent or else very subordinate in Glenshira, must have been something 
entirely different from a local glacier — something to which Glenaray was much exposed, 
and from which Glenshira, on the contrary, was much sheltered. 

The question is then forced upon us — whether there is any distinctive feature in the 
physical geography of the two glens which can afford any explanation to this apparent 
mystery. But the moment this question is asked, we are guided to a most significant reply. 
There is one, and only one, great distinction between the two glens — namely, this : that 
Glenaray terminates in a low pass or watershed only 480 feet above the level of the sea, 
over which the road passes from Loch Fyne to Loch Awe, and that it gapes as with a 
bell-mouthed opening to the valley of Loch Awe in the directions of N. to N.E. Glen- 
shira, on the other hand, is a glen completely closed in that direction by successive ridges 
of mountains, which rise from 1800 and 1600 to at least 2000 feet above the same 
level, and present no pass at all from the valley of Loch Fyne to the valley of Loch Awe. 
Looking up Glenaray from the town of Inveraray, we see a low horizon and the peaks of 
Ben Craachan, on the other side of Loch Awe, fully exposed to view. Looking up Glen- 
shira from a corresponding point at its mouth, our view is bounded by steep mountainous 
ridges, which close it completely, and behind these ridges by a high screen of elevated 
moorland, which constitutes an horizon line of at least 1500 feet high. In short, the 
one circumstance in which the two glens differ is this — that the one is completely open 
and unprotected to an agency moving from beyond it in a north-easterly direction, 
whilst the other glen is completely protected from any such agency by a lofty protecting 
wall of mountains. Of course, the significance of this great difference is immense the 
moment we connect it with the idea that the glaciating agency was floe ice floating 
in a sea which at one time rolled over all our hills up to the level of from 1500 to 
2000 feet, and which, in both its rising and in its falling stages, must, of course, have been 
deflected in its currents by many lower elevations, which would afford complete shelter to 
some glens from the scour to which others, with a lower watershed, were exposed. It 
seems to me that all the differences and peculiarities of these two glens, with reference to 
the marks left by the glacial ages in the one, as compared with the other, are explained 
by the corresponding distinction between them with reference to the physical geography 



200 HIS GRACE THE DUKE OF ARGYLL, K.G., K.T., ON 

of each as now described. And the completeness of the explanation is in no way lessened 
by the fact that the sides, and walls, and floor, of Glenshira are not absolutely devoid of 
marks which have been left by the glacial conditions to which the whole country was at 
one time exposed. Quite near the head of the glen a few mounds of transported blocks 
do appear on the floor of the glen, and the high slopes on each side are thinly sprinkled 
with transported. boulders — not, indeed, with such large and angular masses as encumber, 
in immense profusion, the floor and sides of Glenaray ; but with rounded boulders 
scattered here and there over a wide surface, — as if they had been dropped by floes, 
perhaps gradually melting at great heights overhead, which was then the surface of the 
glacial sea. 

When we stand on the low summit of the road which runs up Glenaray, and try to 
imagine the scene in front of us when the great hollow of Loch Awe was a deep arm of the 
sea, it is not difficult to understand how there must have been a tremendous scouring 
current setting down Glenaray towards Loch ¥yne. Immediately ojDposite to us, on 
the other side of Loch Awe, is the mountain wall of Ben Cruachan, with its subsidiary 
ranges stretching to the N.E. and E. Westward and north-westward there is no such 
barrier — the country is much lower, and a comparatively open sea must have existed in 
those directions. The distant mountains of Morven and Ardnamurchan rise high over a 
series of lower elevations, and those mountains might then have been islands, as the 
Hebridean hills, beyond, are now. To the north-eastward, the mountainous region, 
which so completely protects Glenshira, is traversed by a deep glen, which opens over 
a low pass right across to the eastern side of Scotland — leading first to Loch Tay, and 
beyond that hollow to the continuous valley of the river Tay. Along this deep glen, 
the engineers have constructed the line of railway from Oban to Callander ; and every 
passenger who has an eye to geology must have observed how the line cuts through 
immense accumulations of sand and gravel, with boulder stones profusely scattered over 
all the surfaces of the country. In trying to follow in thought the causes which would 
operate in any submerged area, we must recollect that such conditions involve the double 
operation of a time of sinking or submergence, and a later time of rising, or emergence. 
During both those times, all the natural glens, which cut deeply through the country, 
must have been the seat of powerful currents guided by the containing walls. Thus, the 
low pass, which breaks the wall between Loch Awe and Loch Fyne, would at both epochs 
be a line of scour, and as the emergent movement has been, of course, the latest, its 
marks would be those with which we should expect to meet especially. Accordingly, all 
the facts point to this solution of the appearances presented by Glenaray, which are in 
such remarkable contrast with those of the parallel and adjacent valley of Glenshira. 

There are two other valleys, or shallower glens, in the parish of Inveraray, which 
strongly corroborate the same conclusion as to the glaciating agency which has been at 
work. These are both glens which run parallel to the bed of Loch Fyne, and are parts 
of the series of parallel ridges and. hollows of which the whole mountain mass consists 
that separates Loch Fyne from Loch Awe. Along the last and lowest of these hollows, 



TWO GLENS AND THE AGENCY OF GLACIATION. 201 

the road from Inveraray to Lochgilphead has been made, in order to avoid ground which 
is too precipitous at some places on the shores of Loch Fyne. The summit level 
of the easier gradients afforded by this glen is only 300 feet above the sea, and 
along its floor there are stretches of land which lie very low. These are generally occu- 
pied by mosses, and they are almost entirely free from boulder-stones. But the top and 
sides of the somewhat sudden rise, which conducts us to the summit level, are, on the 
contrary, loaded with transported blocks of stone — some of them more or less rounded, 
but many others presenting rough and angular outlines. The accumulations of these 
which have been left on the more prominent knolls and elevations have all the appearance 
of having been stranded where they now lie by floating ice, which came from the N.E., 
and, in passing, grounded on the first obstructing rocks and shoals which arrested their 
progress through the straits. The same explanation, and no other, is suggested by a 
series of similar blocks which lie on a hill some 500 feet above the same glen. That hill 
happens to be so situated as to break and obstruct a parallel hollow behind the first 
ridge to the north, and it raises its steep front exactly in such a position as to front and 
arrest any agency, whether water or ice, which could have moved south-westward along 
the hollow. Accordingly, this obstructing hill is covered with great angular blocks of 
stone, just as it would naturally be if it stood directly in the way of a current from the 
N.E., which carried along with it floe-ice laden with stones from the N.E. Many 
years ago I took the late Sir David Milne Home to see this remarkable example 
of the transported boulders, to which he devoted so much attention, and he was much 
struck by its significance and its only possible interpretation. 

But even more decisive than all other facts, in my opinion, of the nature of the 
agency which carried the blocks, are the cases of what are called " perched boulders," on 
the very tops of many of the lower ridges, and even of the highest ridge between Loch 
Fyne and Loch Awe. Some of those are very remarkable, both as to great size, as to 
angularity, and as to position. They are so situated that it is impossible to conceive how 
any other agency than floating ice can have placed them where they are. They 
cannot have rolled down from higher ridges behind — because their material is generally 
different, and also because they would have had to roll up steep slopes, and the impetus 
which would be required for this cannot be supposed to have stopped exactly at the top. 
Moreover, many of them are not rolled at all, and some are conspicuously angular. On 
the other hand, such situations are precisely such as would be the natural places, or 
points, of deposit by ice floating on a sea over an emerging land. Every prominence 
which is now a ridge must have been a shoal, or ledge of reef, in such a sea at some 
given time in the process of emergence. Floes, or bergs, stranded on such reefs would 
necessarily drop their burdens upon these when they melted, and such deposit would 
always be upon the very top, or close to it. 

There is yet another very clear indication of the nature of the glaciating agency in the 
appearance presented by the hills on the tops of which these perched blocks are situated. 
In one conspicuous instance, not far from the town of Inveraray, a hill which is crowned 

VOL. XXX VII [. PART I. (NO. 4). 2 D 



202 TWO GLENS AND THE AGENCY OF GLACIATION. 

by a large number of perched blocks, is a granitic ridge, 700 feet above the level of 
the sea, with a steep and partially precipitous face, facing S. and S.E. This face is 
quite untouched, and rough — showing no trace whatever of any rounding or smoothing 
agency having passed along it or down it. But the back of the same hill, facing to the 
N. and N.E., is on the contrary well smoothed and glaciated. Behind and above this 
hill there is another and a much higher ridge, also granitic, which rises to the elevation 
of 1000 feet, and presents, like the lower one, a precipitous face, quite untouched 
by glaciation, towards the S. and S.E. Between the two hills there is a deep hollow, over 
which, in some parts, many huge blocks of transported stones are scattered. These blocks 
also are often very angular and unrolled. It is impossible to reconcile any of these 
facts wdth the agency of any body of ice large enough to rest upon, and to move along, 
the whole surfaces of the country. They are essentially connected with the passage of 
ice in some form which was partial and selective, impinging on all surfaces which were 
exposed to its movement from the N. and N.E., but which admitted of its passing 
entirely over, without any contact, all other surfaces which were not so exposed. 

The evidence, therefore, in favour of the action of floating ice in a glacial sea grounding 
upon and grinding over the rocks and shoals of a rising and emerging land, is accumulative 
evidence, including a great variety of corroborating details. Moreover, it is evidence 
which, so far as I can see, is of such a nature as to exclude the possibility of the action of 
other forms of ice, such as have been suggested in either local glaciers or in an ice sheet. 

I do not deny, nor do I seek to minimise, the great difficulties presented by this 
explanation of a very peculiar set of facts. It involves the idea of a submergence of the 
land, and a re-emergence of it, at some time so recent that in all its main contours or 
outlines the country was very much as we see it now. But the difficulty of conceiving 
such an operation, or rather the difficulty of accounting for it by any known physical 
causes, must not lead us to hesitate in accepting evidence which in itself admits of no 
other explanation. We have to recollect, too, that at least one other explanation, 
namely, that of an ice sheet moving over the whole country, besides failing to account 
for the facts, involves physical difficulties of a much more formidable nature. The 
supposed cause of motion in such a body of ice has never been explained. I believe it to 
be a physical impossibility. This cannot be said of the forces which we must believe 
have acted on the elevation ol our existing islands and continents. They have been 
undoubtedly such as are capable of reproducing like effects at any time. We are, no 
doubt, accustomed to assume that these earth-movements have been sleeping for a far 
longer time, and that, when they did act, they always acted with infinitesimal slowness 
in time and in effects. But this is an assumption in which, very possibly, we may be 
entirely mistaken ; and we have to consider the significant fact that one of the most 
experienced and most cautious of our eminent geologists, Professor Prestvvich, has very 
recently been led to the opinion that some comparatively sudden submergence, and some 
correspondingly rapid re-elevation of the land, has left clear evidence of its occurrence all 
over the south of Europe, at a date quite recent in geological time. 






THE DUKE OF ARGYLL ON TWO GLENS (GLEN ARAT & GLEN SHIRA) 

Rov Soc Eiui r AND THE AGENCY OF GLACIATION. 



Vol. xsxvni 




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( 203 ) 



V. — On the Fossil Flora of the Yorkshire Coal Field. (First Paper.) 
By Robert Kidston, F.R.S.E., F.G.S. (Plates I. -III.) 

(Read 15th July 1895.) 

For many years the Fossil Flora of the Yorkshire Coal Field has been engaging my 
attention, and among the species occurring in that district are many of considerable 
interest. This Coal Field supplied Artis with the specimens which he figured and 
described in his Antediluvian Phytology* 

In 1888, at the Annual Meeting of the Yorkshire Naturalists' Union, held at 
Malton, a committee was formed for the investigation of the Fossil Flora of Yorkshire, 
and since that date four Reports have been prepared and published based upon specimens 
submitted to me for examination by private collectors, and from collections contained 
in public museums.t These Reports only contain lists of the species found, and the 
localities and horizons from which the specimens were derived, with any occasional 
short notes that might have been thought necessary.J All detailed descriptions or 
critical remarks were deferred, and the present paper is the first of what I hope may 
be several, dealing more in detail with the Fossil Flora of the Yorkshire Coal Field. 

Of the many species occurring in this area, none are more interesting than the 
Filicites plumosus, Artis, and the Filicites Miltoni, Artis ; and to the consideration of 
the former of these two species the present paper is devoted. 

Filicites plumosus, Artis, is an extremely variable species, and though this fern 
occurs in many of the British Coal Fields, and is frequent in the Upper and Middle 
Coal Measures, the greater portion of the specimens described and figured in this com- 
munication have been derived from the shales associated with the Barnsley Thick Coal, 
one of the seams of the Middle Coal Measures of Yorkshire, and which is on the same 
horizon as that from which the type specimen of Artis was derived at Elsecar, York- 
shire. It is chiefly for this latter reason that I deal so largely with Yorkshire 

* Antediluvian Phytology, illustrated by a collection of the Fossil Remains of Plants peculiar to the Coal Forma- 
tions of Great Britain. By Edmund Tyrell Artis, F.S.A., F.G.S., London. In all the copies I have seen, the Intro- 
duction to the work is dated 1st September 1825, but the title-page bears the date 1838. This latter date is evidently 
that of a later issue, or second edition of the work, and may only be an alteration of the title-page of the copies sub- 
sequently issued. Each of the twenty-four plates contained in the volume bears the date of 1824. That the work was 
issued at least ten years before 1838 is evidenced by the fact that Brongniaet quotes the book in his Prodrome d'une 
Mstoire des veg&aux fossiles, published in Paris in 1828. Probably, therefore, 1825 is the true date for the first issue 
of the Antediluvian Phytology. 

t The Yorkshire Carboniferous Flora — 

First Report, Trans. York. Nat. Union, part xiv., 1890, pp. 1-64. 

Second Report, „ „ part xviii., 1893, pp. 65-82. 

Third Report, „ „ part xviii., 1893, pp. 83-96. 

Fourth Report (with Index to the four Reports), part xviii., 1893, pp. 97-127. 
\ The names of those to whom the Committee were indebted for assistance are given in these Reports. I am 
however, almost entirely indebted to Mr W. Hemingway for my fine series of Yorkshire specimens of Dactylotheca 
plumosa, Artis, sp., from which largely the present paper has been written. 

VOL. XXXVIII. PART II. (NO. 5). 2 E 



•204 MR ROBERT KIDSTON ON 

specimens in treating of this species, though the Radstock Series of the Upper Coal 
Measures, Somerset, have yielded me my largest and finest barren specimens. 

It is not necessary here to enter into the geology of the Yorkshire Coal Field. 
This has been fully done in the Geology of the Yorkshire Coal Field* and in other 
works dealing with this subject. It may be simply noted that probably all the divi- 
sions of the Coal Measures are present in this Coal Field, — the Upper, the Middle, and 
the Lower Coal Measures, but the Upper Coal Measures are only represented by " Red 
Beds" from which I have not yet seen any specimens, though I believe some plant 
remains have been found in them at Conisborough Pottery. t 

The Middle and Lower Coal Measures contain all the workable seams in this Coal 
Field, but the great coal-yielding series of the Yorkshire Coal Field is the Middle Coal 
Measures. 

The Coal Measures are largely worked in that portion of the county which lies 
around Halifax, Bradford, and Leeds, and which extends southwards to the neighbour- 
hood of Sheffield. 

In 1886 \ I united Dactylotheca {Pecopteris) dentata, Brongt., with Dactylotheca 
[Pecopteris] plumosa, Artis, sp., while preparing the Catalogue of the Palaeozoic Plants 
in the British Museum, and I firmly held this opinion till about three years ago, when 
some specimens submitted to me from Yorkshire led me to believe that Pecopteru 
dentata, Brongt., was specifically distinct from Pecopteris plumosa, Artis, sp. § 

This latter opinion I saw, very shortly after, full cause to reject ; and the points con- 
nected with the fructification, on which I thought the species might be separated, and 
to which I shall more fully refer, were found to be entirely dependent on the position 
of the fruiting portions on the frond and their state or condition of development. 

On the three plates accompanying this paper, figures are given of the typical plant 
as well as of a number of forms of Dactylotheca plumosa, Artis, sp., to which specific 
names have in some cases been given. It is an extremely variable species, — the extreme 
forms differing so much in appearance that they have given rise to the creation of 
several supposed species, all of which, when one has the opportunity of studying a large 
series of specimens, are shown to pass into each other by insensible gradations, and which 
seem to represent only different portions of what must have been a very large frond. 

I have therefore found it quite impossible to draw any line of demarcation between 
what might appear at first sight such distinct forms as Sphenopteris crenata, L. and H., 
on the one hand, and Pecopteris dentata, Brongt., on the other. In fact, these differences 
seem to depend in great measure on whether the fragment is barren or fruiting, and on 
the position it held on the frond of which it originally formed a part. 

Several of the species here placed under the name q{ Dactylotheca plumosa, Artis, sp., 

* Memoirs of the Geological Survey of England and Wales. By A. H. Green, E. Russell, &c. London, 1878. 
t See Kidston, "On the Various Divisions of British Caihoniferous Rocks as determined by their Fossil Flora, 
J'roc. Roy. Phys. Soc. Edvn., vol. xii. p. 210, 1894. 
\ Oatal. Palceoz. Plants, p. 128. 
§ Trans. York Nat. Union, part xviii. p. 106, 1803. 



THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 205 

have been previously united with one or other of the species I regard as synonymous 
with the Yorkshire plant : — 

Dactylotheca, Zeiller, 1883. 

1883. Dactylotheca, Zeiller. Ann. cl. Scienc. Nat., 6 e . ser., 'Bot.', vol. xvi. pp. 184 and 207, pi. ix. figs. 

12-15. 
1888. Dactylotheca, Zeiller. Flore foss. Bassin houil. d. Valenciennes, p. 30, fig. 16. 
1891. Dactylotheca, Kidston. Trans. Geol. Soc. Glasgow, vol. ix. p. 27, pi. ii. fig. 26. 
1877. Senftenbergia, Stur. (not Corda) (in part), Culm Flora, vol. ii. p. 187. 
1883. Senftenbergia, Stur. (not Corda) (in part), Zur. Morph. u. Syst. d. Culm u. Carbonfame, p. 33 (in 

Sitzb. d. It. Akad. d. Wissensch., vol. lxxxviii. Heft i. p. 665). 

Generic description. — Sporangia exannulate, oval or oval acute, formed of elongated 
thick-walled cells, and attached to the secondary veins a little above their point of 
origin. 

Remarks. — The first description of the fruit of Pecopteris dentata, Brongt. 
( = Pec. plwnosa, Artis, sp.), is that given by Zeiller in 1880,* but he did not till 
1883 create the genus Dactylotheca for the reception of this species. 

In 1877 Stur included Pecopteris dentata in the genus Senftenbergia, Corda,t but 
this is clearly an error, for the chief characteristic of the genus Senftenbergia is the 
presence of a very prominent apical annulus, whereas the sporangia of Dactylotheca are 
absolutely devoid of any annulus, even in its most rudimentary form. 

Mons. Zeiller has detected a longitudinal band of narrower cells in the direction in 
which the sporangia appear to have opened at maturity. This longitudinal band I have 
not observed on my specimens, but it can only be seen in one position of the sporangia. 

Dactylotheca is Marattaceous, and amongst recent ferns finds its nearest ally in 
Angiopteris. 

Dactylotheca plumosa, Artis, sp. 
Pis. I.-III. 

1886. Dactylotheca plumosa, Kidston. Catal. Palseoz. Plants, p. 128. 
1890. „ „ ,, Trans. York. Nat. Union, part xiv. p. 36. 

1825. Filiates plumosus, Artis. Antedil. Phytol., p. 17, pi. xvii. 
1.-28. Pecopteris plumosa, Brongt. Prodrome, p. 58. 
^$6.. „ „ „ Hist. d. veget. foss., p. 348, pis. cxxi.-cxxii. 

1869. ,, ,, Roehl. Foss. Flora d. Steink. Form. Westph., p. 88, pi. xxvii. fig. 4. 

1877. Senftenbergia plumosa, Stur. Culm Flora, Heft ii. p. 187 (293). 
1883. ,, „ „ Morph. u. Syst. cl. Culm u. Carbonfame, p. 44. % 

1885. ,, „ ,, Carbon-Flora, I. Fame cl. Carbon-Flora d. Schatzlarer Schichten., 

p. 92, pi. Ii. figs. 1-3. 
1828. Pecopteris dentata, Brongt. Prodrome, p. 58. 

* Ve'get. foss. du terr. houil., p. 87. 

t Corda, Beitr. z. Flora cl. Vorwelt., p. 91, pi. lvii. figs. 1-6, 1867. 

% Sitzb. d. k. z. Akad. d. Wissensch., vol. lxxxviii. Abth. i. p. 633, 



'20(> MR ROBERT KIDSTON ON 

1835. Pecopteris dentata, L. and H. Fossil Flora, vol. ii. p. 201, pi. cliv. 

1836. ,, ,, Brongt. Hist. d. veget. foss., p. 346, pis. cxxiii.-cxxiv. 
1838. „ „ Presl in Sternb. Vers. ii. p. 152. 

1869. „ ,, Schimper. TraitS d. paleont. veget., vol. i. p. 508. 

1879. „ „ Lesqx. Coal Flora, vol. i. p. 240, pi. xliv. fig. 4 (?). 

1880. ,, ,, Zeiller. Veget. foss. d. ten. houil., p. 87, pi. clxviii. figs. 3-4. 

1882. ,, ,, ,, Flore houil. des. Asturies, p. 14.* 

1883. ,, ,, Renault. Cours. d. hotan. foss., vol. iii. p. 121, pi. xxi. figs. 4-5. 

1855. Cyatheites denlatus, Geinitz {in part). Vers. d. SteinJcf. in Sachsen., p. 26, pi. xxix. figs. 10, 12 ; 

pi. xxx. fig. 2. 

1869. „ ,, Roehl. Foss. Flora d. Steink. Form. Westph., p. 87, pi. xxvii. fig. 6. 

1869. Cyathocarpus dentatus, Weiss. Flora d. jiingst. Stic. u. Rothl., p. 86. 

1877. Senftcnbergia dentata, Stur. Culm Flora, Heft ii. p. 187 (293). 

1883. Dactylotheca dentata, Zeiller. Ann. d. Scienc. Nat.. 6 e . ser., 'Bot.', vol. xvi. pp. 184, 207, pi. ix. 

figs. 12-15. 

1883. „ „ „ Bull. Soc. Geol. d. France, 3 e . ser., vol. xii. p. 201. 

1886. Pecopteris {Dactylotheca) dentata, Zeiller. Flore foss. Bassin houil. d. Valenciennes,^. 196 (1888), 

pis. xxvi. figs. 1-2 ; xxvii. figs. 1-4; xxviii. figs. 4-5. 

1892. ,, ,, dentata, var. obscura, Zeiller. Bassin. houil. et perm, de Brive., fasc. ii. ; 

Flore foss., p. 26, pi. ii. figs. 1-5. 

1828. Pecopteris triangularis, Brongt. Prodrome, p. 58. 

1^32. Sphenopteris caudata, L. and H. Fossil Flora, vol. i. p. 137, pi. xlviii. ; vol. ii. p. 157, 

pi. cxxxviii. 

1836. Aspidites caudatus, Gopp. Syst. fit. foss., p. 363. 

1845. Pecopteris caudata, Unger. Synop. plant foss., p. 97 . 

1834. Pecopteris serra, L. and H. Fossil Flora, vol. ii. p. 71, pi. cvii. 

1838. ,, ,, Bresl in Sternb. Vers. ii. p. 159. 

1869. „ ,, Schimper. Traite d. paleont. veget., vol. i. p. 504. 

1877. ,, ,, Lebour. Illustr. of Fossil Plants, p. 47, pi. xxiii. 

1836. A lethopteris serra, Gopp. Syst. fil. foss., p. 302. 

1836. Pecopteris delicahda, Brongt. Hist. d. veget. foss., p. 349, pi. cxvi. fig. 6. 

1838. „ „ Presl in Sternb. Vers. ii. p. 157. 

1869. „ „ Schimper. Traite d. paleont. veget., vol. i. p. 510. 

1848. Cyatheites delicatulus, Bronn. Index pal&ont., p. 364. 

1886. Pecopteris {Dactylotheca) dentata, var. delicalula, Zeiller. Flore foss. Bassin houil. d. Valen- 
ciennes, pi. xxviii. fig. 5, Text, p. 199, 1888. 

1890. Dactylotheca plumosa, var. delicatula, Kidston. Trans. York. Nat. Union, part xiv. p. 36. 

1838. Pecopteris Brongniartiana, Presl in Sternb. Vers., ii. p. 160. 

1834. Sphenopteris crenata, L. and H. Fossil Flora, vol. i. p. 57, pis. c.-ci. 

1869. ,, ,, Schimper. Traite d. pal font, veget., vol. i. p. 379. 

1890. „ ,, Kidston. Trans. York. Nat. Union, part xiv. p. 30. 

1836. Cheilanthites crenatus, Gopp. Syst. fit. foss., p. 248. 

1883. Senftcnbergia crenata, Stur. Morph. u. Syst. d. Culm u. Carbonfarne, p. 44. 

1885. ,, ,, „ Carbon-Flora, I. Die Fame d. Carbon-Flora d. Schatzlarer Schichten, 

p. 72 (pis. xiv. figs. 1, 2, and 3, figures very indistinct). 

1834. Schizopteris adnascens, L. and H. Fossil Flora, vol. i. p. 58, pis. c.-ci. 

1836. Trichomanites adnascens, Gopp. Syst. fil. foss., p. 266. 

1838. Aphlebia adnascens, Presl in Sternb. Vers. ii. p. 113. 

1869. Rhacopihyllum adnascens, Schimper. Traite d. paleont. veget., vol. i. p. 686, pi. xlviii. figs. 1-2 

(fig. 7 (?) )• 

1836. Aspidites silesiacus, Gopp. Syst. fil. foss., p. 364, pi. xxvii. (pi. xxxix. fig. 1. (*?) ). 
1869. Pecopteris silesiacus, Schimper. Traite d. paleont. veget., vol. i. p. 517. 

* Mem. Soc. Ge'ol. du Nord. Lille, 1S82. 



THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 207 

1877. Pecopteris silesiaca, var. Lebour. Illastr. of Fossil Plants, p. 53, pi. xxvi. 

1838. Steffensia silesiaca, Presl in Sternb. Vers. ii. p. 122. 

1854. Pecopteris Glockeriana, Ett. (Gopp. (?) ). Steinkf. v. Radnitz., p. 44, pi. xvii. fig. 1. 

1854. Pecopteris angustifida, Ett. Steinkf. v. Radnitz., p. 45, pi. xvi. fig. 1. 

Description. — Frond very large, much divided, tripinnate or quadripirmate. Pinnae 
alternate. Primary pinna broadly lanceolate. Secondary pinnae lanceolate or linear- 
lanceolate, often slightly overlapping, the central portion the widest, ending in a sharp 
point and slightly narrowed at the base ; the central portion often of about equal width 
for ^ of the length of the pinna. Tertiary pinnae linear-lanceolate, tapering to a 
bluntish apex, the basal portion being usually the broadest. The lower portion of the 
frond probably becomes quadripinnate. The large pinnae are subtended by two stipular- 
like Aphlebia which spring from the anterior and posterior sides of the rachis. These 
are adpressed to the rachis, but, being directed upwards and outwards laterally, hold 
between them the base of the pinna they subtend. In general outline they are deltoid 
or sub-orbicular, and are composed of narrow much divided sharp-pointed linear 
segments without any apparent nervation. 

Pinnules alternate, and varying much in form, size, and pinnule cutting, according to 
the position they hold on the frond being entire, dentate, or divided into teeth-like lobes. 

The pinnules on the middle tertiary pinnae are oval, triangular, or broadly lanceolate, 
with rounded apices, united by their whole base to the rachis. The basal inferior 
pinnule is deltoid — rounded, generally smaller than the others, and occupies the angle 
formed by the insertion of the rachis of the pinna with its parent stem ; it bears a 
distinctly marked lobe on the margin next to the parent rachis. The basal superior 
pinnule is oval or oval-oblong, obtuse, and is the largest pinnule on the pinna. The upper 
pinnules become gradually united in their basal portions and form a more or less lobecl, 
— and finally, an entire blunt apex to the pinna. As the pinnae are traced upwards, 
through the union of pinnules amongst themselves, the pinnae become simply lobed or 
dentate, and in some cases assume the form of oblong or linear entire pinnules. As the 
pinnae are traced downwards towards the base of the frond, the pinnules on the tertiary 
pinnae become more and more distinctly lobed, till they almost assume the form of 
small quadripinnate pinnae. 

The lateral veins in the basal pinnules of the lower tertiary pinnae are generally once 
divided, — in the pinnules of the upper portion, the veins are usually simple ; 
frequently, in the same pinnule, the lower lateral veins are divided, while the upper are 
simple. In the dentate pinnules usually each lobe has a bifurcated veinlet, and in the 
toothed pinnules of the lower pinnae a simple vein runs into each tooth. 

The fructification consists of exannulate oval or oval-acute sporangia, varying in 
length from "50 mm. to *65 mm., and formed of coriaceous elongated cells. The 
sporangia are placed upon, and parallel with, the lateral veinlets at a short distance 
above their point of origin. Frequently the sporangia occupy the whole of the space 
between the midrib and the margin of the pinnule. When the fructification is copiously 



208 MR ROBERT KIDSTON ON 

produced, it results in a partial reduction of the limb of the pinnule. Upper portion of 
the fructifying pinnae barren. 

Rachis rough, with small points from which caducous scales have fallen. 

Remarks. — The fronds of Dactylotheca plumosa, Artis, sp., must have attained to a 
large size. I possess a specimen from Radstock, showing portions of two primary (?) 
pinnae, neither of which is complete, but the most perfect, though it neither shows base 
nor apex, is about 16^ inches long, and has a width of 12 inches, though even here 
the extremities of all the lateral pinnae are broken off. Its complete width could not 
have been less than 18 inches, and was possibly greater. On fronds of this size the 
pinnule cutting must have varied greatly according to the position held by the pinnules 
on the frond. 

The figures which accompany this communication better illustrate the various forms 
of pinnule cutting than could be conveyed by words. From simple pinnules, to others 
divided into sharp tooth-like lobes, all intermediate forms occur, which graduate into 
each other by insensible transitions. On some specimens, the simple undivided pinnule 
is found associated with those divided into prominent saw-like teeth. 

To these polymorphous forms, many specific names have been given, and this is more 
fully referred to in the description of the specimens figured on the plates. 

That these so-called species are only different portions of the same plant — and might 
equally well be fragments of the same frond — will, I believe, be admitted by anyone who 
has had the opportunity of examining such a large and fine series of specimens of 
Dactylotheca plumosa, Artis, sp., which it has been my good fortune to meet with. 

These various forms cannot even consistently be described as varieties, for they only 
represent different portions and conditions of development — barren and fruiting — of 
the same frond ; but should it be thought desirable to distinguish the particular form 
found at any given locality, it can easily be done by indicating the various forms, as 
forma crenata, forma caudata, &c. 

Notes on Specimens figured by various Authors. 

Filicites plumosus, Artis. Antediluvian Phytology, p. 17, pi. xvii. 

Artis, like many of the older and, unfortunately, like some much more recent writers 
on Fossil Botany, gives no enlarged drawings of the details of the pinnule cutting and 
nervation of his Filicites plumosus, and his description is very meagre. Probably, this 
has contributed to the imperfect maimer in which this fern is understood. Of the small 
portion of the fruiting specimen shown on the upper left-hand corner of his plate, he says, 
"Fructification near the margin of the leaflet." This appearance is only shown on im- 
perfectly preserved specimens, of which I possess some similarly preserved from Cooper's 
Colliery, Worsborough Dale, near Barnsley,* to the small fragment figured by Artis. 

* Collected by Mr W. Hemingway. (Reg. No. 2094, &c.) 



THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 209 

Zeiller, in 1883,* in remarking on the polymorphic nature of Pecopteris dentata, 
points out that the Pecopteris plumosa, Brongt.,t was only a form of Pecopteris dentata, 
and that he was inclined to unite to the same species the Pecopteris delicatula, Brongt.J 
That Brongniart was correct in identifying and figuring the plants he named Pec. 
plumosa as Artis' species is beyond all doubt, and the union of Brongniart's figures of 
Pecopteris plumosa with the same author's Pecopteris dentata must carry the Filicites 
plumosus, Artis, along with it. Mons. Zeiller, however, appears to have had some doubt 
as to the correctness of Brongniart's identification of his specimens with Artis' plant. 

Zeiller gives, under the name of Pecopteris (Dactylotheca) dentata, some excellent 
figures of Filicites plumosus, Artis, in his Flore foss. Bassin houil. d. Valenciennes. His 
fig. 2, pi. xxvi., is typical of the form originally described by Artis. His fig. 2, pi. xxvii., 
is also an excellent rendering of the same form, as also are his figs. 3-4 of the same 
plate. His fig. 2, pi. xxvii., corresponds to my fig. 1, pi. i. 

Sphenopteris caudata, L. and H. Fossil Flora, pis. xlviii. and cxxxviii. 

This species is only one of the many forms of Dactylotheca plumosa. I give an 
illustration of the same form on pi. i. fig. 3, from a specimen communicated to me by 
Mr John Ward, Longton, from below the New Mine Coal, the uppermost seam of the 
Lower Coal Measures, Adderley Green, Staffordshire. I possess an identical form (No. 
2108) from the Middle Coal Measures of Yorkshire, collected by Mr W. Hemingway 
from the Thick Coal at Monckton Main Colliery, near Barnsley. 

The other specimen of Sphenopteris caudata which forms the subject of Lindley 
and Hutton's pi. cxxxviii., is preserved in the Hutton Collection, Newcastle-on-Tyne. It 
is not in a good state of preservation, but is evidently the plant named Pecopteris 
dentata by Brongniart. The locality given for this specimen is subject to much doubt ; 
it more probably came from the Somerset Coal Field, as the shale on which the fossil 
occurs agrees with that found in Somerset, but not with the shales which are found at 
Jarrow Colliery, from which the specimen is stated to have come. 

Pecopteris serra (?), L. and H. Illustrations of Fossil Plants. 
Edited by G. A. Lebour. PL xxiii. 

The fossil shown here is a small fragment of Dactylotheca plumosa, with which 
Pecopteris silesiaca, Gopp., sp., the name inscribed in pencil on the original drawing, is 
synonymous. § 

Cyatheites dentatus, Geinitz. Vers. d. Steinkf. in Sachsen, p. 26. 

Of the various figures given by this author, some appear to be doubtfully referable 
to this species. On his pi. xxv. fig. 11, he shows a specimen with Aphlebia attached 

* Bull. Soc. GM. d. France, 3 e ser., vol. xii. p. 201. 

t Hist. d. ve'get. foss., pis. cxxi., cxxii. J Ibid., p. 349, pi. cxvi., fig. 6. 

§ See also Crepin, Bull. Soc. Boy. Bot. Belgique, vol. xx. part ii. p. 25, 1881. 



210 MR ROBERT KIDSTON ON 

to the main rachis. These Aphlebia, which Geinitz identifies as Schizopteris Gutbieri- 
ana, Presl, differ considerably in the wide foliaceous expansion of the segments from any 
Aphlebia of Dactylotheca plumosa ( = D. dentata) that I have hitherto seen. From 
this I am led to infer that probably the fern here figured by Geinitz should not be 
identified with Pec. dentata. 

Also his figures on pi. xxx. figs. 1, 3, and 4, if really referable to this species, are 
misleading and had better be excluded as references ; and if his fig. 4 faithfully repre- 
sents the original specimen it cannot be referred to Pecopteris dentata. 

Schizopteris adnascens. 

Lesquereux, in the Coal Flora, vol. i. p. 321, pi. lvii. figs. 9, 10, and 11, figures and 
describes some Aphlebia under the name of Rhacophyllum adnascens, L. and H. The 
specimens are, however, unassociated with the parent stem, and in this condition it 
appears to me unsafe to identify his specimens with those borne on the rachis of Sphen. 
crenata, L. and H., especially as his figures do not appear to represent a similar Aphlebia. 

I also doubt the accuracy of the reference of the isolated fragment given by 
Schimper in his Traite d. paleont. veget., pi. xlviii. fig. 7, to the Schizopteris 
adnascens, L. and H. 

It is also perhaps advisable to treat in the same way the specimens figured as 
Schizopteris adnascens by Geinitz in his Vers. d. Steinhf. in Sachsen, p. 20, pi. xxv. 
figs. 7-9. 

Heer figures certain ferns which he identifies as the Cyatheites dentatus, Brongt.* 
Possibly he may be correct in his identifications, but if so, the figures are not satis- 
factory. 

Fontaine and White, in their Perm, and Upper Carb. Flora of West Virginia and 
S. W. Pennsylvania, p. 66, pi. xxii. figs. 1-5 (1880), figure and describe a fern they 
refer to Pec. dentata, Brongt. The figures 1, 2, and 4 they provisionally name var. 
crenata, and their fig. 2 var. parva. Their plant, though having some of the characters 
of Pecopteris dentata, Brongt., does not seem to agree well with that species. I have 
not seen any original specimens of their plant, and therefore do not feel justified in 
expressing any definite opinion on its relationship to Pecopteris dentata, Brongt. 

Aspidites silesiacus, Gopp. Syst.Jil.foss., p. 364, pi. xxvii. 

The fine specimen figured by Goppert on his pi. xxvii. is quite indistinguishable 
from Dactylotheca plumosa, Artis, sp. I possess a specimen of Goppert's plant from 
Waldenburg, the original locality for Aspidites silesiacus, which was sent to me some 
years ago by the late Dr Weiss. One of the examples on this specimen completely 
agrees with the form of the plant given on my pi. ii. fig. 9, while another is similar to 
that shown on my pi. iii. fig. 12. The figure given by Zeiller in the Flore foss. Bassin 
houil. d. Valenciennes, pi. xxvi. fig. 2, appears to me to be similar to Goppert's Aspidites 

* Flore foss. Hclv., Lief. i. p. 30, pis. xi. and xii. figs. 1-5, 1876. 



THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 211 

silesiacus according to my specimen from Waldenburg. The enlargements given by 
Goppert fully confirm the identity of his species with Dactylotheca plumosa. His figs. 
2, 3, and 4 correspond to the plant given on my pi. iii. fig. 12, which is a common form 
in Britain, intermediate in character between Filicites plumosus, Artis, and Sphenopteris 
crenata, L. and H. The lower part of Goppert's example is quite typical, Sphenopteris 
crenata, L. and H., and the upper part cannot be distinguished from Pec. plumosa, 
Artis, sp. 

Again Goppert's figs. 6 and 7, especially his fig. 6, has a great similarity to the 
Sphenopteris caudata, L. and H., which is seen in my pi. i. fig. 3. 

The fructification of Goppert's specimen has apparently been imperfectly preserved. 
The only remark he makes about it is that the sori (Fruchthailfchen) are borne on the 
middle of the straight lateral nerves. No description of the sporangia is given. 

Goppert's second specimen, given on pi. xxxix. fig. 1, is too indistinct for criticism. 

The Pecopteris silesiaca, Lebour. Illustrations of Fossil Plants, is the form named 
Sphenopteris crenata, L. and H. } and is seen in my pi. iii. fig. 11, and in the lower 
portion of fig. 13. 

The Aspidites Glockeri, Gopp.,* and var. falcatus, Gopp.,t may very possibly belong 
to the Dactylotheca plumosa, and Schimper unites the type with Pecopteris silesiacus. \ 
Whatever opinion may be held of the specific value of Goppert's original specimens of 
Aspidites Glockeri, I cannot see how it is possible to regard the fern figured by 
Ettingshausen as Pecopteris Glockeriana in his Steinkf. v. Radnitz., pi. xvii. fig. 1, as 
other than Dactylotheca plumosa, Artis, sp. It is to be regretted that Ettingshausen 
has not given any enlarged figures of the pinnule cutting and nervation of his specimen, 
and the description he gives is partially adopted from Goppert. 

The Pecopteris angustiftda, Ettingshausen, given on pi. xvi. fig. 1 of the same work, 
is evidently to be referred to Dactylotheca plumosa, and corresponds to the form shown 
on my pi. i. fig. 1, but his specimen is apparently imperfectly preserved. 

Pecopteris (Dactylotheca) dentata, var. obscura, Zeiller. Bassin houil. et 
perm, de Brive, p. 26, pi. ii. figs. 1-5, 1892. 

In describing this variety Zeiller says : The chief differences between this variety 
and the type are that "the pinnules on the secondary middle pinnae are slightly con- 
tracted at the base and more or less imbricated ; the anterior margin of each pinnule is 
in part covered by the posterior margin of that which lies in front of it ; and further, 
the medial nerve of each pinnule is clearly decurrent at the base, and the secondary 
nerves are almost buried in the parenchyma and difficult to discern." 

"It is chiefly the two last mentioned characters — the decurrence of the medial 

* Syst. fil. foss., p. 375, pi. xxix. tigs. 1-2. 

+ Loc. cit., pi. xxix. figs. 3-4. 

J Traits d. paltfont. vege'L, vol. i. p. 518. 

VOL. XXXVIII. PART II. (NO. 5). 2 P 



212 MR ROBERT KIDSTON ON 

nerve and the obscurity of the secondary veins — which distinguish this form from the 
normal plant. The fructification also differs very little, the limb of the fertile pinnae 
and pinnules, at least on the fossil figured on pi. ii. fig. 2, is much more reduced than 
on the fructifying specimens which I have had from the Middle Coal Measures, but 
perhaps these differences depend simply on the degree of development, and possibly one 
should not attach too great an importance to them." 

" The sporangia are coriaceous, without any trace of an annulus, they possess all the 
characters of the genus Dactylotheca, and they differ from the sporangia of normal 
Pecopteris clentata only in that they are broader and shorter, and, in consequence, 
less tapered, — they are also more numerous and more closely placed the one to the other, 
and they appear to be disposed without any order." 

These differences, as suggested by Zeiller, may only represent a greater advance in 
maturity or a greater development of sporangia. He further refers to a similar occur- 
rence in many species of Asplenium, where, when the fructification is very much 
developed, they cover the whole of the lower surface of the limb.* 

Probably some of my Yorkshire specimens belong to the same form, such as that from 
which the sporangia were drawn, shown on my pi. ii. fig. 14. Here the sporangia, from 
their number and close position to each other, appear as if placed without order. In my 
figure the rows marked a' and a" probably represent the sporangia of one pinnule, and 
were borne on the secondary veins. 

My fig. 2, pi. i., is apparently the barren condition of Zeiller's var. obscura. 

Corresponding with Zeiller's figure of the var. obscura given on his pi. ii. fig. 2, is 
probably my fig. 7, pi. ii. This figure only shows a small portion of a fruiting specimen, 
which is the Bphenopteris crenate, L. and H., so far as the portion figured is concerned, 
but the upper barren portions of the pinnae not shown in the figure, possess all the 
characters of Dactylotheca plumosa. They are quite similar to my fig. 13, pi. iii., only 
not in so good a state of preservation. 

Pecopteris {Dactylotheca) Gruneri, Zeiller. 

Zeiller describes in his Flore fossile : Etudes sur le terr. houil. de Comentry,^ a 
Dactylotheca under the name of D. Gruneri, of which he gives drawings of both the 
barren and fruiting condition. 

This species is certainly very closely related to Dactylotheca plumosa, if really 
specifically distinct from it. 

Comparing it to Pecopteris dentata (which is synonymous with Pecopteris plumosa), 
he says : — "Pecopteris Gruneri, when compared to the Pecopteris dentata ,is distinguished 
by the thickness of its limb, by its pinnules less distinctly lobed, more rounded at the 

* Sterzel, in Die Flora des Rothliegenden im Plauenschen Grunde bei Dresden (Abhandl. d. k. Sax. Gesell. d. Wissen. 
Math. Phys. 01., vol. xi.w, Leipzig, 1893), p. 37, pi. v. figs. 1-G, describes another variety of Pec. dentata under the name 
of var. Saxonica. 

t Page 104, pi. x. figs. 1-2, 1888. 



THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 213 

summit, and finally by the primary pinnae being closer and narrower in regard to their 
length, and by the rachis being always smooth." 

Without examining the original specimens, one is not warranted to propose the 
union of Dactylotheca Gruneri with Dactyloiheca plumosa ; but in this last mentioned 
species the pinnules are entire, dentate, or lobed, according to the position they hold 
on the frond, and the rachis, though typically rough with small points, is, on the 
specimen figured on my pi. ii. fig. 7, quite smooth on one part, whereas another portion 
bears the characteristic little points. On the smooth portions of this rachis the little 
points have probably been obliterated by pressure, but the same cause might have 
equally well removed all evidence of them from the whole of the rachis. 

The Pecopteris Bioti, Brongt., as described and figured by Zeiller in the same work, 
also seems to be very closely related to Dactylotheca plumosa.'* 

Sphenopteris crenata, L. and H., and Aspiclites silesiacus, Gopp. 

Stub, has expressed his opinion that Splien. crenata, L. and H., is identical with 
Aspiclites silesiacus, Gopp., in his paper entitled " Momentaner Standpunkt meiner 
Kenntniss uber die Steinkohlenformation, Englands." t 

That Pecopteris dentata belonged to Pecopteris plumosa was suspected by Eoemer 
when he wrote his Beitr. z. geol. Kennt. des nordw. Harzgebirges in 1860.J 

Description of Specimens of Dactylotheca plumosa, Artis, sp., figured in the 

ACCOMPANYING PLATES I.-III.§ 

PI. I. figs. 1 and la. 

Specimen from Monckton Main Colliery, near Barnsley, Yorkshire. Horizon. — 
Barnsley Thick Coal. Middle Coal Measures. || 

This may be regarded as the typical form of Filicites plumosus, Artis. The ultimate 
pinnae are linear or linear-lanceolate, with alternate pinnules. The inferior basal pinnule 
is placed in the angle formed by the union of the rachis of the ultimate pinna with 
the stem from which it springs, and is always smaller than the immediately succeeding 
pinnules. On the lower pinnae, it is generally composed of two lobes, the foremost of 
which is usually sub-triangular, blunt, large, and the other — that next the stem which 
bears the pinna — is rounded and slightly smaller. The corresponding pinnule on the 
upper pinnae is sub -triangular and simple, and fills up the angle formed by the union of 
the rachis of the pinna to its parent rachis, being united by its base in part to both. 
The basal superior pinnule is large and usually slightly larger than any of the succeeding 
pinnules. It is oblong-lanceolate, with an acute or slightly rounded point. The 

* hoc. cit., p. 99, pL ix. figs. 2-4. 

t Jahrb. d. k h. geol., Reichsanst, 1889, vol. xxxix. Heft i. p. 5. 

I Palceont, vol. ix. p. 34, 1860. 

§ I have figured small specimens, to enable me to give a greater number of forms. 

|| The same horizon as that from which the type of Filicites plumosus was derived. 



•214 MR ROBERT KIDSTON ON 

pinnules arc directed slightly forward, and are entire or slightly crenulate at the 
margin (fig. la). The pinnules are rarely free, being generally united below. The 
lateral veins of the lower pinnules usually divide once ; those of the upper pinnules are 
simple. The degree of distinctness with which the veins are visible depends in great 
measure on the condition of preservation of the fossil, but they appear to have been 
somewhat immersed in the parenchyma of the limb. 

PI. I. figs. 2, 2a, and 2b. 

From the same Horizon and Locality as fig. 1. 

This specimen appears to be the same type as that figured by Zeiller as var. 
obscura* The pinnules are broader in proportion to their length, and placed close 
together ; the anterior border of the pinnule in its lower portion has a tendency to over- 
lap the posterior margin of the pinnule in front of it. The pinnules are oblong- 
triangular, with rounded apices (fig. 2a), or oblong-linear, with sharp points. Their 
form alters according to the position they hold on the pinna, and whether the pinna) 
belong to a higher or lower portion of the frond. The lateral veins are simple or 
bifurcated, according to the position of the pinnules on the pinna. The superior and 
inferior basal pinnules (fig. 2b), in their position and shape, conform to the characteristics 
which mark the type. 

PL I. figs. 3 and 3a. 

From Adderley Green, near Longton, Staffordshire. Horizon. — Below the New 
Mine Coal, which is the uppermost seam in the Lower Coal Measures of the Potteries 
Coal Field. 

This is the Sphenopteris caudata, L. and H. Fossil Flora, vol. i. pi. xlviii. The 
other specimen which they figure under the same name in vol. ii. pi. exxxviii., is, I 
think, the Pecopteris dentata, Brongt., but the original, which is contained in the 
" Hutton Collection," is badly preserved. 

The penultimate pinnae are linear-lanceolate and slightly overlapping. The 
ultimate pinnae are narrow linear-lanceolate, distant from each other, and especially so 
in the upper portion of the penultimate pinnae. 

The pinnules are sub-triangular, directed forwards, and united to each other below. 
The inferior basal pinnule is smaller than the superior basal one (fig. 3a), which is 
always the largest and longest on the pinna. 

The form and direction of the pinnules give a saw-like appearance to the pinnae. 
The nervation is not shown.t 

PI. I. figs. 4, 4a, and 45. 

From Monckton Main Colliery, near Barnsley, Yorkshire. Horizon. — Shale over 
Barnsley Thick Coal. Middle Coal Measures. 

This interesting specimen shows in the pinna? of the upper portion the typical form 
of pinnule and nervation of Filicites plumosus. The lower pinnae, on the other hand, 

* Bassin houil. dfcrm. de Brive., p. 26, pi. ii. figs. 1-5. 

+ My thanks arc due to Mr John Ward, Longton, for this specimen. 



THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 215 

seem indistinguishable from Asplenites ophiodermaticus of Goppert, as figured on his 
plate xvii. figs. l-2. # My enlarged fig. 4a seems similar to his enlarged fig. 2. The 
ultimate pinnae are linear, alternate ; the pinnules are bluntly oval, or shortly pointed. 
The pinnules on the basal part of the pinnae are almost upright on the rachis ; those 
about two-thirds up, and above this point, are directed slightly forwards towards the 
apex of the pinnae. The pinnules are very closely placed, and the anterior margin of 
the pinnule slightly overlaps the posterior margin of the pinnule in front of it. They 
are united to each other at their bases, and this united portion forms a narrow wing 
along the rachis. The posterior basal pinnule is smaller than the others, and occupies 
the angle caused by the union of the pinna and its parent rachis (fig. 4a) ; the superior 
basal pinnule is, on the other hand, the largest on the pinna. By a gradual diminution 
of the lobing as the pinnae recede from the basal portion of the specimen towards the 
apex, we find the position of the compound pinnae (a) (on fig. 4), taken by small simple 
pinnae (6) (on fig. 4), bearing first lobed or dentate (6'), and then entire pinnules (fig. 
46), having all the characters of typical Filicites plumosus. These upper pinnules are 
homologous with the ultimate pinnae of the lower part of the specimen. The rachis 
is rough. 

SiuR,t among other species, unites with Asplenites ophiodermaticus, the Sphen- 
opteris caudata, L. and H., pi. xlviii. This last-mentioned plant is certainly to be 
referred to Filicites plumosus, and very probably so should Goppert's Asplenites ophio- 
dermaticus, but not having seen any authentic specimens of Goppert's plant, I prefer, in 
the meantime, to leave the union of this plant with Filicites plumosus an open question. 

Perhaps Brongniart's fig. 3, pi. cxxiii.,| is the same form of the species as that 
given here on my pi. i. fig. 4. 

PI. II. figs. 5, 5a, and 56. 

From Woolley Colliery, Darton, near Barnsley, Yorkshire. Horizon. — Barnsley 
Thick Coal. Middle Coal Measures. 

This specimen is the Sphenopteris crenata, L. and H. The fossil shows the upper 
surface of the frond, but, at parts where the carbonaceous film is removed, the fructi- 
fication is very beautifully shown. The pinnules are divided into narrow obtuse teeth- 
like lobes, as seen in the enlarged fig. 5a, the nervation of which is obscure. 

The sporangia are beautifully preserved ; one is shown magnified 26 times at fig. 56. 
They exhibit no indication of an annulus. 

The sporangia are placed so close together on the pinnules that they seem to occupy 
the whole of the dorsal surface, and frequently the two halves of the pinnule are con- 
duplicately bent upon each other, in which case it is impossible to discover the original 
position of the sporangia, but they appear to have been placed almost parallel with the 
veins. The sporangia are about 0'65 mm. in length. 

* Syst. fil. foss., p. 280, 1836. 

t Die Carbon-Flora d. Schatz. Schichten, p. 78, 1885. 

| Hist. d. v&je't. foss. 



216 MR ROBERT KIDSTON ON 

PL II. fig. 7. 

From Monckton Main Colliery, near Barnsley, Yorkshire. Horizon. — Barnsley 
Thick Coal. Middle Coal Measures. 

The specimen shows portion of a primary (?) pinna, and the fragment preserved is 
26 cm. long. The rachis at its thickest part is about 7 cm. broad. 

At certain parts of the rachis the little rough points are almost entirely effaced — 
probably from pressure — which, at other portions, are distinctly preserved, and this 
shows how much the absence or presence of such characters depends on the condition of 
preservation. 

The plant is the Sphenopteris crenata, L. and H., but is not so well preserved, as far 
as the lateral pinnae are concerned, as those shown at figs. 5 and 13. The specimen is 
a fruiting one, of which only a portion is shown natural size. It is similar to the fossil 
given at fig. 13. The upper ultimate pinnae (not shown in the figure) are barren, and 
bear simple pinnules, of which some have simple and others bifurcated veins, identical 
with those shown at fig. la, fig. 45, and fig. 13a, and which are typical Filicites plumosus. 
It is, therefore, seen that under certain conditions, when the sporangia are copiously 
produced, it results in the limb of the pinnules being more or less reduced. In the case 
of fig. 5, and in certain of the pinnae of figs. 7 and 13, the reduction of the limb has 
reduced the pinnules to narrow teeth-like lobes, leaving only that portion of the limb 
on which the sporangia themselves are placed. This example also shows very beauti- 
fully the Aphlebia (originally supposed by Lindley and Hutton to be a parasite, and 
named by them Schizopteris adnascens), arising from the rachis at the points where 
the pinnae are given off. 

Mons. Zeiller has shown,* from specimens collected at Larche, that the Aphlebia 
which occur on the rachis are disposed in pairs at the origin of the Aphlebia bearing 
pinnae, — one on the anterior, and the other on the posterior face of the rachis. They 
may thus be compared to two wing-like structures that arise from the back and front of 
the rachis, and bending upwards and outwards embrace the base of the pinna they 
subtend between them. 

The Aphlebia are bipinnately divided into sharp-pointed lanceolate segments. 

Zeiller has observed a similar arrangement of the Aphlebia on Diplothmema Zeilleri, 
Stur.t 

PI. II. fig. 6. 

From the same Locality and Horizon as the last. 

This fossil shows an early state of development of several pinnae, — what might be 
called the " Spirorbis " condition of the plant, — where the pinnae are still spirally coiled. 
The Aphlebia, however, appear to be fully developed, and therefore probably acted as 
protective organs to the more tender and immature portions of the frond. 

* Bassin houil. et perm, de Brive., p. 26, pi. ii. figs. 3-4. 
t Flore f oss. Bassin hovil. d. Valenciennes, pi. xvi. fig. 1. 



THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 217 

PL III; fig. 10. 

This example, from the Barnsley Thick Coal, near Barnsley, shows natural size some 

of the largest Aphlebia of Filicites plumosus which I have yet seen. Their surface is 

finely striated in the direction of growth, but there is no clear indication of any 

nervation. 

PL III. figs. 13, 13a, 136, and 13c. 

From Monckton Main Colliery, near Barnsley, Yorkshire. Horizon. — Barnsley Thick 
Coal. Middle Coal Measures. 

This specimen combines in the same example the characters of Sphenopteris crenata, 
L. and H., and Filicites plumosus, Artis. The upper part is the Filicites plumosus, Artis 
(fig. 13a), while its lower portion is the Sphenopteris crenata, L. and H. (figs. 13c and 136). 

The fossil is a fruiting example ; but as only the upper surface of the pinnules is 
exhibited, the presence of the sporangia are only shown indistinctly through the tissue 
of the pinnules. This example corresponds to one of the lateral pinnae, the basal portions 
of which only are shown on pi, ii. fig. 7, but it is much better preserved in regard to the 
minute structure of the pinnules. Fig. 13a shows two pinnules from the upper barren 
pinnae, which are entire with simple veins. 

It cannot be doubted that these dentate pinnules are formed by a reduction of the 
tissue of the limb through the development of a copious fructification. Were the upper 
portion of this specimen separated from the lower part, the upper would, without doubt, 
be labelled Pecopteris plumosa, whilst the lower portion would be named Sphenopteris 
crenata by those who regard these two as distinct species. The rachis is roughened by 
the customary little points. 

PL III. figs. 11, 11a, and 116. 

From Shropshire. Middle Coal Measures. (Exact Locality and Horizon uoknown.) 
This fossil is the Sphenopteris crenata, L. and H. On the other hand, it approaches 
somewhat, in the small lobes of the long narrow pinnules, to the Sphenopteris caudata 
of the same authors (vol. i. pi. xlviii.).* The specimen is well preserved and shows the 
nervation in some of the pinnules. In the basal lobes the vein bifurcates, or the lobe 
has a central vein giving off lateral branchlets (fig. 116). In the upper lobes the veins 
are simple (fig. 11a). The specimen exhibits the upper surface of the frond, and shows 
no indication of bearing sporangia, though the form of the pinnules is that which is 
frequently associated with fructification in this species. 

The basal pinnae have six or seven pairs of rounded lobes and a long tapering blunt 
apical lobe (fig. 11a), but the upper pinnae have only a few pairs of rounded lobes at 
their base, while the uppermost ones are entire. 

PL III. figs. 12, 12a, and 126. 

From South Kirby Colliery, near Pontefract, Yorkshire. Horizon. — Barnsley Thick 
Coal. Middle Coal Measures. 

* See also my fig. 3, pi. i. 



218 MR ROBERT KIDSTON ON 

This is one of those forms which stands intermediate in character between Sphenop- 
teris crenata, L. and H., and Pecopteris plumosa, Artis, and which it is very difficult to 
refer to either one or the other, but, in its general aspect, it has perhaps a greater 
similarity to Sphenopteris crenata. The rachis is roughened with small points. 

On the ultimate pinnse the inferior basal pinnule is very small and composed of two 
lobes, — a larger subtriangular one, with a smaller lateral rounded lobe next to the main 
rachis. The basal superior pinnule is longer than the succeeding pinnules, and on the 
lower pinnae bears several pairs of rounded lobes (fig. 125). The corresponding pinnule 
on the upper pinnse bears a few lobes at the base (fig. 12a). A central vein gives off 
lateral veinlets to each lobe. 

PI. II. fig. 14x28. 

From Monckton Main Colliery, near Barnsley, Yorkshire. Horizon. — Barnsley Thick 
Coal. Middle Coal Measures. 

This figure shows a few sporangia magnified 28 times, from another specimen 
belonging to the Sphenopteris crenata form of the same species. This specimen shows 
how the sporangia are placed on the pinnules. Each of the small lobes had a row on 
each margin, the sporangia lying at right angles to the midrib. Thus, in fig. 14, the 
central vein ran between the two rows marked a' and a", but most probably the spor- 
angia were placed on lateral veinlets, which sprang from this central vein, and which 
have now disappeared. I think this is shown from the nervation preserved in figs. 11a 
and 116, pi. iii. 

The sporangia drawn show some groups from which all trace of the limb has been 
removed, and which have probably adhered to the counterpart of the block containing 
the fossil, thus leaving only the sporangia attached to the matrix of the specimen in my 
possession. 

The sporangia, which are beautifully preserved and show well the cell structure, are 
oval in form, and measure on an average about 0'50 mm. in length. They are absol- 
utely devoid of all trace of an annulus. Had an annulus been present even in a most 
rudimentary form, from the excellent state of preservation of the sporangia on this and 
on several other examples in my possession, it could not have escaped observation. 

The sporangia on all my specimens are more oval than those described by Zeiller in 

the Flore foss. Bassin houil. de Valenciennes, pi. xxvi. fig. 2, and in the Ann.d. Scienc. 

Nat, 6 e ser. ' Bot.', vol. xvi. pi. ix. figs. 12-15, 1883, but they agree in form with those of 

his Dactylotheca dentata, var. obscura* The general character of Zeiller's fig. 2, pi. ii., # 

in the copious manner in which the sporangia have been produced and the absence of 

the limb, shows a great resemblance to such specimens as those figured on my pi. ii. 

figs. 5, 7, and 14. 

PI. II. figs. 9, 9a, 96, and 9c. 

From Monckton Main Colliery, near Barnsley, Yorkshire. Horizon. — Barnsley 
Thick Coal. Middle Coal Measures. 

* Flore foss. Bassin houil. et perm, de Brive., p. 26, pi. ii. figs. 2, 2a, 26, aud 2c. 






THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 219 

This example shows the arrangement of the sporangia on the pinnules. In this 
specimen the pinnules are oblong, obtuse, and entire, and placed close to each other. 
The nervation is obscure, but apparently the lateral veins have bifurcated, and each arm 
has borne a sporangium (figs. 9a and 9b). On these smaller pinnules the sporangia 
occupy the whole space between the midrib of the pinnule and its margin, and were 
parallel with the course of the lateral veinlets — in fact, were placed on them. 

The sporangia are oval, but the apex is slightly more pointed than the base. They 
measure about 60 mm. long. Their walls are composed of elongated coriaceous cells 
without any indication of an annulus. Fig. 9c shows a sporangium magnified 25 
times. 

PI. II. figs. 8 and 8a. 

From the same Locality and Horizon as the last. 

This small specimen shows the barren condition of the form usually associated with 
the name of Pecopteris dentata, Brongt. , and is similar to that given by Zeiller in his 
Flore foss. Bassin houil. d. Valenciennes., pi. xxvi. fig. 1. The basal inferior pinnule 
is small and lobed, and occupies the angle formed by the union of the rachis with the 
parent stem. The superior basal pinnule is, on the other hand, the largest on the pinna. 
The nervation is not well shown, and seems to be immersed in the tissue of the pinnule. 
The rachis is rough. 

Specimens from Cooper's Colliery, Worsborough, near Barnsley, Yorkshire. 
Horizon. — Barnsley Thick Coal. Middle Coal Measures (Reg. Nos. 2093-2100). 

These specimens occur on a light grey coloured shale, but are not so well preserved 
as those already described. They exhibit a slightly larger form of the plant, and the 
sporangia are slightly longer and proportionally narrower than those shown in my figures. 
They are not, however, so sharply pointed as those given by Zeiller in the original 
description of his genus Dactylotheca. It was upon these differences that I presumed 
that Pecopteris plumosa might be specifically distinct from Pecopteris dentata, but 
I have since seen that what I thought might prove a distinguishing character does not 
hold, as these slight variations in the size and form of the sporangia appear to depend 
on the position of the pinnules and pinnae on the frond on which the sporangia 
occur. 

Distribution in Britain. 

Dactylotheca plumosa occurs in the Upper, Middle, and Lower Coal Measures. It 
attained its maximum period of development in the Upper Coal Measures, and though less 
frequent in the Middle Coal Measures it is still comparatively common. In the Lower 
Coal Measures, however, it has all but disappeared, and from this division I only know of 
four specimens, two of which are those figured by Lindley and Hutton, — one as Sphenop- 

vol. xxxviii. part ii. (no. 5). 2 G 



220 MR ROBERT KIDSTON ON 

tern crenata (pi. xxxix.), and the other as Sphenopteris caudata (pi. xlviii.). The two 
remaining Lower Coal Measure examples are one from Fife and the other from the 
Potteries Coal Field, North Staffordshire (PI. I. fig. 3.) 

Scotland. 

Lower Coal Measures. 
Fife :— 

Locality. — East Wemyss. {Forma crenata.) (J. Kirkby.) 
Horizon. — Lower Coxtool Coal. 

England. 

Upper Coal Measures. 
Somersetshire : — * 

Localities. — Kilmersden Pit, near Radstock. 

Braysdown Colliery, near Radstock. 
Tyning Pit, Radstock. 
Wellsway Pit, Radstock. 
Upper Conygre Pit, Timsbury. 
Lower Conygre Pit, Timsbury. 
Old and New Pits, Camerton. 
Horizon. — Radstock Series. 

Middle Coal Measures. 
Lancashire : — 

Locality. — St Helens. (Rev. H. H. Higgins.) 

Horizon. — Ravenhead Coals. 
Locality. — Dixon Fold, Stoneclough, near Manchester. (J. W. Croston.) 

Horizon. — A little above Doe Mine. 
Locality. — Ashton, near Manchester. (Brongniart.) 

Horizon. — (1). 
Locality. — Oldham. ( Brongniart. ) 

Horizon. — (?). 
Locality. — Worsley. 

Horizon. — Basscy Mine. (28 yds. above Ramshorn Mine.) 
Locality. — Oldham Edge, Oldham. (J. Nield.) 

Horizon. — " Forest bed." (16 yds. below Hollingworth Mine of Oldham.) 
Derbyshire : — 

Locality. — Claycross. (Rev. J. M. Mello.) 

Horizon. — (?). 

*The forma denUda is much more common tban any other in the Upper Coal Measures. 



THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 221 

South Staffordshire. (Dudley Coal Field) : — 

Locality. — Doulton's Marl Pit, Netherton, near Dudley. (H. W. Hughes.) 

Horizon. — Blue Measures. (6 ft. above Fire Clay Coal.) 
Locality. — Eussell's Hall, Dudley. (H. W. Hughes,) 

Horizon. — Roof of Fire Clay Coal. 
Yorkshire : — 

Localities. — Monckton Main Colliery, near Barnsley. {Type and forma 

dentata.) (W. Hemingway.) 
East Gawber Colliery, near Barnsley. {Type and forma dentata and crenata. 

(W. Hemingway.) 
Woolley Colliery, Darton, near Barnsley. {Type and forma crenata. 

(W. Hemingway.) 
Elsecar, Wentworth. (Type of Artis. ) 

Horizon. — Barnsley Thick Coal. 
South Kirby Colliery, near Pontefract. {Forma dentata and type. 

(W. Hemingway.) 

Horizon. — Barnsley Thick Coal. 
Locality. — Cooper's Colliery, Worsborough, near Barnsley. (W. Hemingway. 

Horizon. — Rock over Barnsley Thick Coal. 
Locality. — Wheatley Wood Colliery, near Barnsley. (W. Hemingway. 

{Forma crenata.) 

Horizon. — Winter Coal. 
Worcestershire : — * 

Localities. — Railway Cutting, immediately west of Dowles, Railway Bridge 

Forest of Wyre. (T. C. Cantrill.) 

Horizon. — (?). 
Cooper's Mill, Dowles Valley, Forest of Wyre. (T. C. Cantrill.) 

Horizon. — (?). 



Lower Coal Measures. 
Durham : — 

Localities. — Jarrow Colliery. (Type ofSph. crenata, L. and H., pi. xxxix., also 

of Pec. caudata, L. and H., pi. xlviii.).t 

Horizon. — Bensham Seam. 
North Staffordshire (Potteries Coal Field) : — 

Localities. — Adderley Green, near Longton. {Forma caudata.) (J. Ward.) 

Horizon. — Below the New Mine Coal. 

* I have also seen the crenata form from the Forest of Wyre, but do not know the exact locality from which the 
specimen was collected. 

t Note. — The other specimens of Splienopteris crenata, L. and H. (pis. c.-ci.), came from the Whitehaven Coal Field, 
but I have hitherto been unable to visit this Coal Field, so can express no opinion as to their age. 



222 MR ROBERT KIDSTON ON 



EXPLANATION OF PLATES. 
Plate I. 

Fig. 1. Dactylotheca plumosa Artis, sp. (Typical form). Loc. Monckton Main Colliery, near Barnsley, 
Yorkshire. Hor. Barnsley Thick Coal. Middle Coal Measures. Natural size. W. Hemingway, Collector, 
Reg. No. 2107. Seep. 213. 

Fig. la. Two pinnules, x 4. 

Fig. 2. Dactylotheca plumosa, Artis, sp. (Pecopteris dentata, Brongt.). Loc. Monckton Main Colliery, 
near Barnsley, Yorkshire. Hor. Barnsley Thick Coal. Middle Coal Measures. Natural size. W. Heming- 
way, Collector. Reg. No. 2112. See p. 214. 

Fig. 2a and 26. Pinnules, x 4. 

Fig. 3. Dactylotheca plumosa, Artis, sp. (Pecopteris caudata, L. and H.). Loc. Adderley Green, near 
Longton, Staffordshire. Hor. Below New Mine Coal. — The uppermost seam in the Lower Coal Measures. 
Natural size. J. Ward, Collector. Reg. No. 357. See p. 214. 

Fig. 3a. Pinnule, x 4. 

Fig. 4. Dactylotheca plumosa, Artis, sp. Loc. Monckton Main Colliery, near Barnsley, Yorkshire. Hor. 
Shale over Barnsley Thick Coal. Middle Coal Measures. Natural size. "W. Hemingway, Collector. Reg. 
No. 2111. Seep. 214. 

Fig. 4a. Portion of pinna, x 4. 

Plate II. 

Fig. 5. Dactylotheca plumosa, Artis, sp. (Sphenopteris crenata, L. and H.). Fruiting specimen. Loc. 
Woolley Colliery, Darton, near Barnsley, Yorkshire. Hor. Barnsley Thick Coal. Middle Coal Measures. 
Natural size. W. Hemingway, Collector. Reg. No. 1215. See p. 215. 

Fig. 5a. Pinnule, x 4. 

Fig. 5b. Sporangium, x 26. 

Fig. 6. Dactylotheca plumosa, Artis, sp. Circinately coiled up specimen showing the Aphlebia. (Schizop- 
teris adnasceus, L. and H). Loc. Monckton Main Colliery, near Barnsley, Yorkshire. Hor. Barnsley 
Thick Coal. Middle Coal Measures. Natural size. W. Hemingway, Collector. Reg. No. 1212. Seep. 216. 

Fig. 7. Dactylotheca plumosa, Artis, sp. (Sphenopteris crenata, L. and H, and Schizopteris adnascens, L. 
and H.). Portion of a large specimen showing the Aphlebia attached to the rachis at the point of insertion 
of the pinnae. Loc. Monckton Main Colliery, near Barnsley, Yorkshire. Hor. Barnsley Main Coal. Middle 
Coal Measures. Natural size. W. Hemingway, Collector. Reg. No. 1210. See p. 216. 

Fig. 8. Dactylotheca plumosa, Artis, sp. Loc. Monckton Main Colliery, near Barnsley, Yorkshire. Hor. 
Barnsley Thick Coal. Middle Coal Meaaures. Natural size. W. Hemingway, Collector. Reg. No. 2105. 
See p. 219. 

Fig. 9. Dactylotheca plumosa, Artis, sp. Fruiting specimen. Loc. Monckton Main Colliery, near 
Barnsley, Yorkshire. Hor. Barnsley Thick Coal. Middle Coal Measures. Natural size. W. Hemingway, 
Collector. Reg. No. 2088. See p. 218. 

Fig. 9«. Two pinnules, showing the arrangement of the sporangia. 

Fig. 9 b. Another pinnule, showing the sporangia. 

Fig. 9c. A sporangium, x 25. 

Fig. 14. Dactylotheca plumosa, Artis, sp. Sporangia, x 28 from another specimen which shows the 
Aphlebia attached to the rachis. Loc. Monckton Main Colliery, near Barnsley, Yorkshire. Hor. Barnsley 
Thick Coal. Middle Coal Measures. W. Hemingway, Collector. Reg. No. 2092. See p. 218. 

Plate III. 

Fig. 10. Dactylotheca plumosa, Artis, sp. Aphlebia (Schizopteris adnascens, L. and H.). Loc. Near 
Barnsley, Yorkshire. Hor. Barnsley Thick Coal. Middle Coal Measures. Natural size. W. Hemingway, 
Collector. Reg. No. 2110. See p. 216. 



THE FOSSIL FLORA OF THE YORKSHIRE COAL FIELD. 223 

Fig. 11. Dactylotheca plumosa, Artis, sp. (Sjphenopteris crenata, L. and H.). Loc. Shropshire. Hor. 
Middle Coal Measures. Natural size. Reg. No. 966. See p. 217. 

Fig. 11a. Ultimate pinna, x 4. 

Fig. 116. Two pinnules, showing nervation more highly enlarged. 

Fig. 12. Dactylotheca plumosa, Artis, sp. (Approaching the form named Sphenopteris crenata, L. and 
H.). Loc. South Kir by Colliery, near Pontefract, Yorkshire. Hor. Barnsley Thick Coal. Middle Coal Mea- 
sures. Natural size. W. Hemingway, Collector. Reg. No. 2109. See p. 217. 

Fig. 13. Dactylotheca plumosa, Artis, sp. Portion of a specimen, showing the organic union of typical 
" Filiates plumosus, Artis," and Sphenopteris crenata, L. and H. Loc. Monckton Main Colliery, near Barnsley, 
Yorkshire. Hor. Barnsley Thick Coal. Middle Coal Measures. Natural size. W. Hemingway, Collector. 
Reg. No. 2101. See p. 217. 

Fig. 13a. Two pinnules from the upper portion of the specimen corresponding to the " Filiates plumosus, 
Artis," x 4. 

Figs. 136 and c. Two pinnules from a lower part of the specimen corresponding to the Sphenopteris 
crenata, L. and H. 

Note. — All the figured specimens are in the author's collection. 



'rans.Roy. Soc.Edin? Vol. XXXVIII. 

KlDSTON, ON THE FOSSIL FLORA OF THE YORKSHIRE COALFIELD. PI. I. 




KUston. 



7. HutiuEitiiT Biiitf 



DACTYLOTHECA PLUMOSA, Artis sp 




\ 



ns.Roy. Suc.Edm 1 " Yol.XXXVlII. 

KlDSTON, ON THE FOSSIL FLORA OF THE YORKSHIRE CoALpIELD. PI. II. 




R jdston 



DACTYLOTHECA PLUMOSA, At t i s 



sp. 



.ov. Soc.Edin 1 



Vol. XXXVIII. 



KlDSTON, ON THE FOSSIL FLORA OF THE YORKSHIRE COAL FlELD. PI. [II, 




F.Huth.LitWE'dm 1 



DACTYLOTHECA PLUMOSA, Artis sp. 



( 225 ) 



VI. — Experiments on the Transverse Effect and on some Related Actions in Bismuth. 

By J. C. Beattie. (With a Plate.) 

(Read 17th December 1894.) 

Section I. — Introduction. 

Clerk Maxwell, in his Electricity and Magnetism, vol. i. § 304, makes the 
following remark about the rotatory coefficient : — " It should be found, if anywhere, in 
magnets which have a polarisation in one direction, probably due to a rotational 
phenomenon in the substance." 

The current which should arise from such a coefficient was first observed by 
Hall. He passed a current through a strip of metal ; he then found two points on 
opposite sides of the strip, which, while the current was flowing, were at the same 
potential, and which therefore indicated no current when joined to a galvanometer. 
The plate was next brought into a uniform magnetic field, and when everything was 
steady the two points previously at the same potential were no longer so, and a current 
flowed through the galvanometer. This effect is observable in all conductors. 

Kundt * has shown that in iron, nickel, cobalt, it is proportional to the magnetisation. 
Whether this is true for the diamagnetic metals has not, so far as I know, been definitely 
settled yet. But, should this be proved, we have a comparatively easy method for 
studying the magnetisation in these metals. 

Another phenomenon which may advantageously be studied by means of the trans- 
verse effect is the variation of resistance of conductors carrying a current in a magnetic 
field. Goldhammer t has shown in another way that the increase or decrease of the 
resistance in bismuth is proportional to the square of the magnetisation, and suggests 
that the same may be true for cobalt and nickel. Evidently the proportionality or non- 
proportionality for these two latter metals can be settled at once by comparing the 
variation of resistance and the transverse effect at the same field strength ; and, 
similarly, the same method can be employed to show whether or not the variation of 
resistance bears any relation to the magnetisation in all cases where it has first been 
proved that the magnetisation and the transverse effect are proportional. So far as I 
know, this method has not as yet been tried experimentally. I propose in another paper 
to give some results relating to this matter. 

In bismuth the transverse effect has not yet been proved to be proportional to the 
magnetisation ; nor, indeed, is it certain that the so-called transverse effect in bismuth is 
a pure Hall effect, \ or is caused by a number of separate effects. As I shall show later, 
the transverse effect in most cases is really the sum of three effects. 

* Wiedemann's Annalen, 1893, Bd. 49, S. 257. t Wiedemann's Armalen, 1889, Bd. 36. 

\ By Hall effect is meant a transverse effect proportional to the first power of the magnetisation. See " On Rela- 
tion between the Variation of Resistance in Bismuth, &c," Trans. R.S.E., vol. xxxviii. 

VOL. XXXVIII. PART I. (NO. 6). 2 H 



226 MR J. C. BEATTIE ON THE 

The following experiments were carried on in the Ph}^sicalisches Institut, Muenchen ; 
and I have to thank Professor Boltzmann for the trouble he put himself to, for his 
suggestions, and for placing the whole resources of his laboratory at my disposal. 

The plates used were cast from two separate quantities of ordinary mercantile 
bismuth. In some instances they were cooled quickly, in others slowly. The thicknesses 
varied from three to one millimetre ; the ratio of length to breadth was about three to 
one as the plates were originally used ; afterwards these dimensions were considerably 
modified. 

The galvanometer used was a Wiedemann, with a Siemens well-formed magnet. 
The electro-magnet used for the creation of the magnetic field consisted of two 
cylinders of soft iron 60 cm. long, 16 cm. in diameter, placed on a parallelepiped of 
the same material 63 cm. long, 20 cm. high, 20 cm. broad. The shoes were formed by 
two blocks 16 cm. square, 20 cm. long, to which truncated cones were fixed with a 
base diameter of 16 cm., a summit diameter of 6 cm. Each cylinder was surrounded by 
two spools, round which the copper wires were wound. Diameter of the wire 2" 5 mm. ; the 
total length of wire was 3850 mm. ; the number of windings 5951. (Cp. fig. A, Plate P.) 
The current to the electro-magnet was supplied by an accumulator battery of 
56 cells. 

The strength of the field was measured by Verdet's method. A wire was arranged 
in the form of a square, the ends were inserted into the galvanometer circuit, and 
when the electro-magnet was on, the square which was kept perpendicular to the 
lines of force was pulled quickly out of the field. 

The readings thus obtained were compared with those obtained from an earth 
inductor inserted in the same circuit, and the strength of the field in absolute units 
arrived at in the usual way. To get the strength of the field in absolute units, the 
numbers given as field strengths in the results must be multiplied by 138 "5. 

The strength of the current which flows in the direction of the plate's length — and 
which will be called the primary current — w r as measured at the beginning and end of 
each series of experiments. For this purpose a thick copper wire was inserted in the 
primary circuit. To two points of this, copper wires were soldered, which, by means of 
a commutator could be placed in the galvanometer circuit when necessary. 

The electro-magnet was so placed that it exercised a minimum effect on the galvano- 
meter, which was at a distance of thirty or forty feet. The magnet and primary 
currents could both be reversed by commutators ; the number of readings necessary to 
eliminate disturbing effects was thus four. The average of the four readings was divided 
by the primary current strength : this quantity is called later the transverse effect. 

The positive direction of the transverse effect is so defined : Let the plate of bismuth 
be supposed to be in the plane of the paper with the north pole of the magnet above, the 
south below, the paper. Then, if in going from the point where the primary current 
enters to that where the transverse current enters the motion is counter clock, we call the 
transverse effect positive. 



TRANSVERSE EFFECT AND ON SOME RELATED ACTIONS IN BISMUTH. 227 

In diagram B, Plate P, with dotted circle to represent north pole above the paper, 
the transverse effect is positive. 

To both ends of the plates strips of copper of the same breadth and thickness were 
soldered ; to these latter, wires were soldered, which lead to the accumulators giving the 
primary current. 

To two points in the middle of the sides of the bismuth plates w T ires were soldered ; 
each wire was doubled on itself, the point of contact with the bismuth forming the bottom 
of a V. Between the arms of the V mica was inserted to insure insulation. Both arms 
were kept in the plane of the bismuth plate and perpendicular to its length. One arm 
of each was joined to the galvanometer ; the other led to a mercury pool in the first 
series of experiments, in the later ones it was unconnected. (Fig. C, Plate P.) 

Section II. — On the Effect on the Transverse Current of Inserting a Shunt 
whose Resistance is of the same Ob der of Magnitude as that of the Plate. 

The transverse effect has up till now always been measured with a galvanometer whose 
resistance was many times greater than that of the plate of metal experimented upon. 
The question arises, How will this current be affected when a shunt is inserted between 
the transverse electrodes whose resistance is of the same order of magnitude as that of 
the plate ? If the plate when placed in a steady magnetic field behaves as a cell with 
constant electromotive force would do, it will divide according to Ohm's law ; if, on the 
other hand, it behaves as a cell whose electromotive force is not constant, the current 
will not be obtainable from the equation — 

„, Electromotive Force 

Current = = — =— - . 

Resistance 

For example, Prof. Lommel, in his paper " Sichtbare Darstellung der aquipoten- 
tialen Linien in durchstromten Platten. Erklarung des HaH'schen Phanomens," # has pro- 
posed a formula, according to which the insertion of a shunt between the two transverse 
electrodes would not affect the reading on a galvanometer whose resistance is great — com- 
pared with the sum of the resistances of the bismuth plate and of this shunt. 

Each plate experimented upon was placed between the poles of the electro-magnet, 
perpendicular to the lines of magnetic induction. 

Before the magnet was put on, a current from the accumulators at A was sent through 
the plate. Two points, E and D, as near the middle as possible, were then found, so that 
when wires joined them to the galvanometer G, no current passed. From E and D two 
other wires lead to the mercury pools L and M respectively. Should it be found 
impossible to find two points at the same potential, the current which goes through the 
galvanometer circuit can be eliminated by joining E and N or D and N, as the case may 
be, and inserting a suitable resistance. (Cp. fig. D, Plate P.) 

* Sitzungsbericht der Kong, bayerischen Akedamie der Wissenchaft, 1892, Bd. xxil. Heft iii. § 371. 



228 



MR J. C. BEATTIE ON THE 



A series of five experiments was made with each field strength. In 1st, 3rd, and 5th 
E L M D was open, in 2nd and 4th E L M D was closed.* The average of the first three 
was then divided by that of the 2nd and 4th. 

Next, the resistance of the bismuth plate was measured when the electro-magnet was 
on. A current was sent by A in the direction A L E D M A, or vice versa, and E and D 
were joined to the galvanometer ; four readings were taken — the resistances of the copper 
wires L E, M D and of the short wire L M — the total being of the same order of magni- 
tude as that of the bismuth plate. These measurements were made at the beginning and 
end of each series of five experiments. 

Let C be the transverse current when E L M D is open, let S be the resistance of the 
shunt ELMD, n that of the bismuth plate. Then theoretically we have 

C 



Current when ELMD is open 
Current when E 1/ M D is closed 



c/n 



1/n+lls 

i+? 

But since we have measured n and s directly, we can calculate 1 + " ; the calculated 
and the observed values will agree, if the transverse effect is of the same nature as the 
current obtained from a cell of constant electromotive force. 

The following are some of the results obtained : — 



Plate (Ia). 



Length, 

Breadth, 

Thickness, 



5-63 

2-9525 

0T94I3 



cm. 



This plate was quickly cooled in casting ; the temperature of the room was in all the 
experiments about 15° C. Made from first supply of bismuth. 




Plate (Ib). 

Length, .... 

Breadth, .... 

Thickness, .... 

Slowly cooled. Made from first supply of bismuth. 



6-045 

2-58 

0-12235 



cm. 



* The galvanometer reading obtained in this case, divided by the strength of the primary current, is called in 
the results the shunted transverse. 



TRANSVERSE EFFECT AND ON SOME RELATED ACTIONS IN BISMUTH. 



229 



Feld Strength. 


Trans. Current. 


Shunted Trans. 
Current. 


Trans. Current. 
Shunted Trans. 


1+5 

Calculated. 


118-0 
140-0 
148-0 


-0-14253 
-0-20239 
-0-22356 


-0-0666 

-009329 

-0-10174 


2-138 
2-169 
2-197 


2-118 
2-150 

2-159 



Plate II. 
Length, .... 
Breadth, . ... 

Thickness, .... 

Slowly cooled. Made from first supply of bismuth. 



6-26 

2-945 

0-149725 



cm. 



Field Strength. 


Trans. Effect. 


Trans. Effect 
with Shunt. 


Trans. Effect. 
Trans. Shunted. 


1+5 

Calculated. 


36-0 

61-0 

120-0 

137-8 

146-0 


-0-19674 
-0-25164 
-0-30315 
-0-30779 
-0-31051 


-0-09929 
-0-14596 
-0-13744 
-0-12963 
-0-11821 


1-981 
1-724 
2-203 
2-374 
2-626 


1-947 

1-76 

2-186 

2-357 

2-489 



The dimensions of the plate were next altered ; in particular the thickness was 
considerably reduced by planing. It was now 

0-0827 cm. 



Field Strength. 


Trans. Effect. 


Trans. Effect 
with Shunt. 


Trans. Effect. 
Trans. Shunted. 


i+;- 

Calculated. 


28-2 

66-7 

147-0 


-0-37519 

-0-57451 
-0-70719 


-0-18141 
-0-25566 
-0-25157 


2-068 
2-247 
2-8111 


2-062 

2-25 

2-826 



Plate III. 
This plate was of pure bismuth, specially prepared by Professor Classen in Aacheo. 
Length, . . . . . 1-99 

Breadth, ..... 1-075 

Thickness, ..... 0-126975 



cm. 



Field Strength. 


Trans. Effect. 


Trans. Effect 
with Shunt. 


Trans. Effect. 
Trans. Shunted. 


l+l 

Calculated. 


9-4 
55-0 
100 
138-2 
146-0 
153-0 


-0-05219 

-0-16162 

-0-22199 

-0-27166 

-0-2812 

-0-28849 


- 0-03953 

-0-113 

-0-14378 

-0-16375 

-0-16676 

-0-17034 


1-320 

1-430 

1-543 

1-658 

1-6777 

1-6936 


1-327 
1-415 
1-539 
1-660 
1-679 
1-6929 



230 



MR J. C. BEATTIE ON THE 



Plate VI. 
Rapidly cooled ; made from first supply of bismuth. 

Length, ..... 

Breadth, ..... 

Thickness, ..... 



5-81 

2-9935 

0-14105 



cm. 



Field. 


Trans. Current. 


Trans. Current 
Shunted. 


Trans. Current. 

Trans. Current 

Shunted. 


Calculated. 


48-4 

87-2 

118-0 


-0-0185 
+ 0-05646 
+ 0-11916 


- 0-0075 
+ 0-02206 
+ 0-0461 


2-4666 
2-5628 
2-5845 


2-4671 
2-5621 

2-558 



Plate VII. 

Slowly cooled ; made from first supply of bismuth. 

Length, ..... 
Breadth, ..... 
Thickness, ..... 



6-032 
1-507 
0-06713 



Field. 


Trans. Current. 


Trans. Current 
Shunted. 


Trans. Current. 

Trans. Current 

Shunted. 


1+5 

Calculated. 


17-8 
121-6 
140-0 

147-8 


-0-2536 
+ 0-1852 
+ 0-22024 
+ 0-2484 


- 0-00883 
+ 0-06045 
+ 0-07243 
+ 0-08184 


2-872 
3-0637 
3-0407 
3-0352 


2-8979 
3-0667 
3-0805 
3-0543 



Plate VIII. 

Quickly cooled ; made from new supply of bismuth. 

Length, . 

Breadth, .... 

Thickness, .... 



5-99 
3-03 
0-3153 



cm. 



Field. 


Trans. Current. 


Trans. Current 
Shunted. 


Trans. Current. 

Trans. Current 

Shunted. 


1+2 

Calculated. 


41-4 

80-2 

100-0 

123-3 


-009817 
-0-108 
-009986 
- 009026 


-0-0651 
-006846 
-0-06144 
-0-05554 


1-5077 
1-5775 
1-6253 
1-6251 


1-5016 
1-5799 
16251 
1-6475 



It will be seen from a comparison of the last two columns in the different results that 



TRANSVERSE EFFECT AND ON SOME RELATED ACTIONS IN BISMUTH. 231 

the agreement between the observed and the calculated values of 1 + * is in most cases 
close ; the discrepancies can be quite well accounted for by experimental errors in 
measuring such small resistances. 

Section III. — On the Change of Sign of the Transverse Effect. 

In Plate 1. it was noticed that the transverse effect attained a maximum and then 
decreased steadily with increasing fields. Other plates were then made, to see if this result 
was observable in them ; and in some of them the maximum was reached with com- 
paratively weak fields. With stronger fields the transverse current decreased, till finally 
it vanished ; with still stronger fields it reappeared again, but with the opposite direction. 

With Plate VI., as originally prepared, the following results were obtained : — 



Field. 


Transverse Effect. 


Sign. 


Rotatory Coefficient. 


3-5 


01179 




3-83 


5-0 


•01648 


- 


3-74 


11-5 


•0302 


- 


2-99 


19-0 


•03595 


- 


2-15 


22-0 


•03993 


- 


2-06 


32-0 


•03787 


- 


1-35 


400 


•03183 


- 


0-88 


48-4 


•0185 


— 


0-43 


53-0 


•01625 


- 


0-35 


60-0 


0032 


- 


06 


65-0 


•0057 


+ 


0-1 


776 


•03432 


+ 


05 


87-2 


•05646 


+ 


0-74 


118-0 


11916 


+ 


1*15 


127-2 


•14305 


+ 


1-28 



Here the transverse effect is at first negative ; it increases, till with a field strength 
between 22 x 138 '5 and 32 x 138 "5 in c.g.s. units, it reaches a maximum. After that it 
decreases and finally vanishes between 60 and 65. It begins again, however, with increas- 
ing fields, and continues to increase ; but now it has the opposite sign. The rotatory 
coefficient has its greatest — and negative — value with the weakest field. 

This same plate was next shortened and narrowed, but the thickness kept as before. 
The transverse effect was again observed ; it was still the same in character. It vanished 
with the same field strength as in the previous experiment ; and with weak fields was 
negative, with strong positive. 

Next the plate was made thinner by planing, and the following results were obtained : — 



Plate VI. 



Length, 

Breadth, 

Thickness, 



4-22 
2-36 
0-0657 



cm. 



232 



MR J. C. BEATTIE ON THE 



Field. 


. Transverse Effect. 


Sign. 


Rotatory Coefficient. 


23-4 


0-08714 




1-97 


29-0 


0-09326 


- 


1-70 


35-2 


0-08958 


- 


1-35 


41-8 


0-08033 


- 


1-02 


45-0 


0-06857 


- 


0-081 


69 


Not observed. 






80-0 


0-03144 


+ 


0-21 


102-8 


0-12287 


+ 


0-63 


1100 


0-20363 


+ 


0-88 



A comparison of these results with those obtained with the original plate shows that 
the maximum negative effect is reached with a higher field, and that the field strength 
for which the effect vanishes is also higher. If we take the magnetic force as abscissa, 
the transverse effect as ordinate, we may express the result by stating that the curve 
giving the relation between the two has been moved, so that it cuts the axis at a point 
farther along in the positive direction. 

See graph of curve giving relation between transverse effect and field strength in 
fig. 3, where A is the curve for the plate as originally cast, B that after it was hammered, 
C that after it was planed down. 

Finally, the dimensions of the plate were again slightly modified, and, in addition, it 

was hammered. 

Plate VI. 
Length, . . . . . 3 -25 cm. 

Breadth, . . . . . 1-24 

Thickness, ..... 0-0657 „ 



Field. 


Transverse Effect. 


Sign. 


Rotatory Coefficient. 


49-0 


0-1075 




1-16 


66-1 


0-08014 


— 


0-64 


76-0 


0-0394 


- 


027 


85-0 


Not observed. 






123-1 


0-12246 


+ 


0-527 


134-0 


01657 


+ 


0-66 



In this instance the reversal of sign takes place with a still stronger field. An attempt 
to further thin the plate proved abortive ; it was now so brittle that planing caused it 
to break. 

In Plate VII. the reversal was also observed in the plate as originally made ; the effect 
disappeared with a field strength of 43 x 138"5 c.g.s. It was then halved and the trans- 
verse effect for both halves was observed, and was found to vanish for the same field 
strength. Finally, one half was hammered ; the same results — negative for the weaker 
fields, positive for the higher — were obtained, but the vanishing did not now take place 
until a field strength 60 x 13 85 was reached. 



TRANSVERSE EFFECT AND ON SOME RELATED ACTIONS IN BISMUTH. 233 

Plate Ib also showed this reversal. For the original plate the following results were 
obtained : — 



Plate Ib. 



Length, 

Breadth, 

Thickness, 



6-045 

2-58 

0-12235 



cm. 



Field. 


Transverse Effect. 


Sign. 


Rotatory Coefficient. 


8-0 


0-0302 




3-72 


15-1 


0-05276 


- 


3-45 


28-0 


0-05517 


- 


1-94 


38-0 


0-0484 


- 


1-26 


59-0 


0-0218 


- 


0-36 


63-0 


0003 


- 


0-046 


75-6 


0-02229 


- 


0-29 


118-0 


0-14253 


+ 


1-19 


140-0 


0-20239 


+ 


1-43 


148-0 


0-22356 


+ 


1-49 



The transverse effect is first negative ; it increases and reaches its maximum negative 
effect with field strength 28 (about). Afterwards it decreases and vanishes with field 63 
(about). It again appears and increases for all other fields higher than 63, but now has 
the opposite direction. 

This plate was next varied in length and in breadth, but the same thickness was 
retained ; and the transverse effect was found to vanish for the same field strength. 

The plate was then hammered, and it was found that the transverse effect did not 
vanish until a field strength of about 80 was reached ; the field strength by which the 
maximum negative effect was reached was also greater. 

The plate was now made thinner by planing — 



Length, 
Breadth, 
Thickness, 



4-47 
2-08 
0-0665 



cm. 



Field Strength. 


Transverse Effect. 


Sign. 


Rotatory Coefficient. 


26-0 


0-21699 




4-48 


38-0 


0-22231 


- 


3-14 


49-0 


0-21172 


_ 


2-32 


62-0 


0-13521 


— 


1-17 


87-0 


0-4749 


— 


0-29 


97-0 


Not Observed. 






101-0 


0-0376 


+ 


0-199 


117-8 


0-17013 


+ 


0-77 


135-0 


0-27122 


+ 


1-08 


145-0 


0-33084 


+ 


1-22 



VOL. XXXVIII. PART I. (NO. 6). 



2 I 



234 



MR J. C. BEATTIE ON THE 



We see that a still stronger field is now required to make the transverse effect vanish ; 
and for the maximum negative effect also a stronger field is necessary than in the former 
cases. 

Finally, the plate was again hammered, and the following results obtained : — 



Field Strength. 


Transverse Effect. 


Sign. 


Rotatory Coefficient. 


50-0 


023289 




2-5 


70-0 


016731 


- 


1-28 


100-0 


0-01837 


- 


0-098 


1056 


0-02256 


+ 


0-115 


123-5 


0-11556 


+ 


0-502 


1430 


0-21119 


+ 


0-79 



which again shows a considerable increase in the field necessary to reverse the direction 
of the transverse current. 

The reversal of direction was not observed in Plates II. and III., nor was a maximum 
effect reached in these two plates : In Plate I., again, no reversal was found, but a maximum 
effect was reached with a field strength a little over 100. 

Another series of plates was now made from a new supply of mercantile bismuth. 
Two Plates, VIII. and IX., were made each about 3 mm. thick ; VIII. was cooled quickly, 
IX. slowly. The transverse effect was negative throughout ; it reached a maximum in 
both cases, and then began to decrease ; but it could not be made to vanish by field 
strengths at disposal. 

Two other Plates, X. and XL, were made, each about 1*5 mm. thick; X. was 
cooled quickly, XI. slowly. In these two plates the transverse current vanished, and 
with higher fields had the opposite sign positive. 

Another Plate, XII., was made in the form of a cross ; to the two arms of the cross 
the galvanometer wires were soldered, and the effect of the soldering on the plate as a 
whole minimised. (Cp. fig. E.) With this plate the following results were obtained: — 



Plate XII. 



Length, 
Breadth, 
Thickness, 



6-22 
1-85 
0-10462 



Field Strength. 


Transverse Effect. 


Sign. 


Rotatory Coefficient. 


25-2 


0-17158 




5-74 


34-6 


0-18389 


— 


4-48 


45-5 


018115 


— 


3-36 


88-3 


0-05617 


- 


0-538 


1030 


0-0119 


+ 


0-097 


116-5 


006051 


+ 


0-438 


137 


0-16766 


+ 


1033 


145-0 


0-20602 


+ 


1199 



TRANSVERSE EFFECT AND ON SOME RELATED ACTIONS IN BISMUTH. 235 

We may sum up the results as follows : — With thick plates the transverse current 
does not change its direction for any strength of field, though in some cases a maximum 
value is reached and passed ; nor can the change of direction be brought about by 
planing, hammering, or modifying the dimensions of the plates. Cp. fig. 1, which gives 
the relation between field and effect for Plate 1a, and fig. 2, which gives the same for 
Plate II. 

With thinner plates the transverse current is positive for strong fields, negative for 
weak ones. The field strength at which vanishing takes place is the same for the same 
plate, so long as it is modified only in length and breadth ; but if the plate be planed 
down, the field at which the current vanishes is stronger than in the original case. 
Similarly, if the original plate be hammered, the field required to produce vanishing is 
stronger : a combination of hammering and planing raises very considerably the strength 
of the field required. From a comparison of the results, it will be seen that in different 
plates the transverse current vanishes for different fields. Cp. fig. 3, where the three 
curves give the relation between field strength and transverse effect for Plate Ib ; A refers 
zo the original plate, B to the same plate hammered, C to it after planing. 

This reversal of the transverse current has already been observed by Von Ettings- 
hausen and Nernst * in an amalgam of bismuth and tin. 

In the one certainly pure bismuth, Plate III., the ratio of the increase of resistance to 
the square of the transverse effect, was practically constant ; this is as it should be, if in 
diamagnetic bodies the transverse effect is, as in the magnetic metals, proportional to the 
magnetisation I, and the increase of resistance proportional to, I 2 . If we start from this 
and apply it to those plates in which the transverse effect vanishes, we find that our 
facts do not tally with our assumptions. For if the transverse current be proportional 
to the magnetisation, when the former vanishes, so must the latter and so must the 
increase of resistance too : that is, when the transverse current vanishes, the resistance 
of the bismuth at the same field strength must be the same as when no field is present. 
But for Plate Ib. the following results were obtained : — 



Field Strength. 


Resistance Proportional to. 


Transverse Effect. 


o-o 

28-0 

63-0 

118-0 

147-7 


254-0 
265-4 
280-1 
300-2 
312-0 



-0-5517 
- 0-003 
+ 0-14253 
+ 0-22356 



That is, the transverse effect vanishes at about 63, but the resistance increase is at the same 
field strength quite perceptible. Another effect observed in all the plates and which will 
be later described, supports the view that the increase of resistance does not vanish with 



Sitz. bericht der kais. Akad. der Wissenschaft, ii. A.bth., 1887, Bd. 96. 



236 



MR J. C. BEATTIE ON THE 



the transverse effect. From this we may draw three conclusions : — (l) The two assump- 
tions are both wrong ; (2) one is wrong ; (3) or we may still suppose both true, and 
assume that in bismuth two constants with opposite signs are involved in the transverse 
effect. That is, instead of assuming that it is proportional to the vector product of the 
primary current and the magnetisation, we assume that it is the vector product of the 
primary current and (cj + c 2 I 3 ). 

In the first case we may write the electromotive force 

where Cj is negative for bismuth and those metals which have a negative transverse 
effect ; positive for those which have a positive effect. 
In the second case 

e = Yu(c 1 l + c 2 l s ) 

where c x is the same constant as before, c 2 is another constant positive in the first class of 
substances negative in the second. In those substances in which the transverse effect is 
proportional to the magnetisation, c 2 is infinitesimally small in comparison with c x ; in 
bismuth and any other substances where this is not the case, c 2 has such a value that for 
sufficiently high fields the transverse effect may vanish, and for still higher reverse its 
direction. Similarly, c 2 might be of such magnitude that the transverse effect did not 
vanish, but still reached a maximum value, and then began to decrease as in Plate Ia, 
fig.l. 

The validity of this assumption could be tested by determining the magnetisation 
directly, and thus determining c x and c 2 for different field strengths. 



Section IV. — On Effects other than the Transverse Effect proper. 

Two other such effects were observed. The first was evident in the whole of the 
plates experimented upon. In the plate of pure bismuth, III., it was such, that when 
the apparatus was arranged, as in diagram (D), in passing from the entrance of the 
primary current at B to that of the effect at D, the motion was counter-clockwise. It 
changed with the change in direction of the primary current, but not with the 
reversal of the magnet. Thus, with one arrangement of the magnet, it acted against the 
transverse current ; in the other with it. In Plate III. it acted against the transverse 
current when the north pole of the magnet was in front of the diagram, with it when the 
south pole was in front. 

The following results were obtained with Plate III. : — 



Field, 
Effect, 


55-0 
003613 


100-0 
0-08908 


138-2 
0-14475 


153 
0-16332 



TRANSVEESE EFFECT AND ON SOME RELATED ACTIONS IN BISMUTH. 237 

To find how this effect varied with the primary current strength, the field was kept 
constant, while the primary was varied : — 



Primary Current 
Proportional to. 


Effect in Scale Parts. 


Effect. 
Primary. 


60-0 
124-1 
187-0 
373-0 


90-0 
177-6 
269-4 
515-4 


1-5 
1-43 
1-44 
1-39 



or the effect is, for the currents used, practically directly proportional to the primary 
current. 

This effect had the same direction in Plate II., for which the following results were 
obtained : — 



Field, . 
Effect, . 


36-0 



•61-0 
0-0045 


120-0 
0-0509 


137-0 
0-07175 


146-0 
0-084 



In Plate XII. again the direction of the effect was the opposite. In the other plates 
it had sometimes the one direction, sometimes the other ; indeed, after a plate had been 
planed or hammered, it sometimes had the opposite direction to that in the original plate. 
So long as it was less in magnitude than the transverse effect proper, its disturbing 
influence was eliminated by making four different experiments, according as the direction 
of the field or the primary current was varied. Should it, however, have a greater 
value than the transverse current, this was no longer the case ; and when the transverse 
current vanished, it alone was observable ; it increased in all cases with the field strength, 
and in no case did it change sign, unless the plate was modified. 

The existence of an effect whose direction can in no case be predicted follows from 
the general equations for a non-isotropic body. For, suppose we have an isotropic body 
which is brought into a magnetic field and carries a current, it is acted on by mechanical 
forces. The body becomes anisotropic, and the transverse coefficients of resistance are 
brought into play ; a transverse current flows, whose direction is determined by the 
structure of the body. Or, suppose the body to be originally non-isotropic, a transverse 
current will be observed with no magnetic field present ; this, however, can be eliminated 
by the insertion of a proper resistance. When the magnet is excited, the transverse resist- 
ance is modified, so that the inserted resistance no longer balances it. Result is, the 
transverse current again appears. The fact that it does not depend on the direction of 
the field shows that the resistance concerned is proportional to some even function of the 
magnetisation. 



238 



MR J. C. BEATTIE ON THE 



The equations for such a body would be 



X = r n u + r 12 v + r 13 w 
Y = r 12 w + r 22 v + r 23 w 



'13" 



'23" 



'33" 



If to this we add the fact that a magnetic field gives rise to a rotatory coefficient as 
well, which is an odd function of the magnetisation, we have the most general equations 

X = r n u + r 12 v + r 13 w + T 3 v - T 2 w> 
Y = r 12 u + r 22 v + r 23 to + TjW - T 3 ?< 
Z = r 13 u + r 23 v + r 33 w + T 2 w - Tj« 

where x, y, z are the components of the electromotive force parallel the three axes ; 
u, v, iv the components of the current ; p n , r 22 , r 3S the direct resistances ; r 12 , r 13 , r 23 the 
transverse resistances ; T u T 2 , T 3 the rotatory resistances. 

The second effect was not observed in all the plates. Its presence was observed by 
the gradual decline of the galvanometer deflexion of the transverse current, which lasted 
for about a minute, when a steady state was usually reached. It was measured in the 
following manner : — After the steady transverse reading had been taken, the electro- 
magnet was kept on, the primary current was broken, and the galvanometer immediately 
inserted. The reading thus obtained was usually small and died away gradually. In 
every instance it was oppositely directed to the transverse current. 



Plate I. 



Length, 

Breadth, 

Thickness, 



5-45 

2-96 
0-1305 



cm. 



Field, 
Effect, 


9-6 
0-0069 


36-8 
0-0319 


58-0 
00437 


119-0 
0-0429 


131-5 

0-0381 


141 

0-0371 



The numbers given under " effect " are here, as before the galvanometer reading, 
divided by the primary current. 

The same plate was previously used, its thickness then being 0'19416 cm. 



Field, . 


24-0 


52-2 


98-0 


114-2 


131-0 




, Effect, . 


0-0213 


0-0288 


00334 


0-0343 


0-03133 








Plate ] 


[I. 






] 

] 
1 


jength, 

3readth, 

"hickness, 


• 


* * 


6-26 cm. 
2-945 „ 
0-1497 „ 


, 




Field, . 


36-0 


61-0 


120-0 


137-0 


146'0 




Effect, . 


0-01746 


0-0343 


0-0718 


0-0806 


0-084 





TRANSVERSE EFFECT AND ON SOME RELATED ACTIONS IN BISMUTH. 239 
The same plate planed to thickness, 0'08277 cm. 



Field, 




15-7 . 


28-2 


66-7 


94-2 


110-0 


147-0 


Effect, 




0-0068 


0-02114 


0-0608 


0-0878 


01045 


0-122 




Plate III. 






Length, .... 


1-99 cm. 




Breadth, .... 


1-075 




Thickness, .... 


0-12697 „ 


Field, 




98-0 


138-0 


146-0 


153 


Effect, 




0-0362 


006246 


0-06349 


006904 


The 


same plate was planed to thickness, 0*09 cm. 




Field, 


. 


33-8 


61-0 


93-2 




110-0 


1530 


Effect, 


• 


0-0125 


0-03061 


0-04977 


00609 


0-06831 



It will be observed that in Plate I. a maximum effect is reached just as was the case 
with the transverse effect in that plate ; and in II. and III. no such maximum effect 
was reached again agreeing with the transverse current. 

The same effect was observed and measured in Plates VIII. and IX. ; in those plates 
which gave a reversal of the transverse current ; the result was too small tb be measured 
accurately. In some cases, however, it was noticeable and always directed against the 
transverse current. In those plates in which the effect was observed, it must be added 
to the transverse effect to give the latter its proper value. 

To find how this effect depended on the current, the field was kept constant, and four 
different currents used. 



Primary Current in Scale Parts. 


Effect in Scale Parts. 
Primary in Scale Parts. 


60-0 
124-1 
187-1 
3730 


0-06458 
0-06305 
0062 
0-06246 



or for the currents used, the effect is proportional to the current. 

To explain this effect we must remember that the body carrying the current in a 
magnetic field is subject to mechanical force and is also heated by the current. Accord- 
ing to Joule's law the heating is proportional to the square of the current strength ; it 



240 TRANSVERSE EFFECT AND ON SOME RELATED ACTIONS IN BISMUTH. 

cannot, therefore, be due to this heating effect, otherwise its direction would be independent 
of that of the primary current. We must rather suppose that it is the result of a kind 
of Peltier effect, arising from the heating of a substance differently deformed in different 
parts. Should this be so, it might be possible to map out a plate into pressed and 
stretched regions by observing the direction of the effect in different parts of the plate. 

For let us assume, after Bidwell,* that the plate is deforming in the following manner 
so that A B represents a compressed part, B F a stretched, and so on ; then if the electrodes 
are at L and M, the current is in the direction L M ; should they be at N and the 
current would be in the direction N 0, — that is opposite to the former (fig. F). 

If such be the explanation, we should expect to find an electromotive force created in 
a heated body when it is placed in a magnetic field ; this has been observed by Ettings- 
hausen and Nernst.1' 

* Phil. Mag., 1884. 

t Wiedemann's Annalen, 1887, Bd. 31. 






oc. Edin. Vol. XXXVIII 

Mr. J. C. Beattie on the Transverse Effect in Bismuth. 




Field. 



Fig. 1. 



Fig. 2. 



(b) -H> 



T 




Fig. 3. 





(E) 




(f) 



L F O 



(A) 





1 6 CMS. 


J r 6cM s 




Q 












L 








t=r 
















c= 


60 CMS. 
1 6 CMS. 


-{=. 










i. , 














. 63 CMS. _ 















( 241 ) 



VII. — On the Relation betiveen the Variation of Resistance in Bismuth in a Steady 
Magnetic Field and the Rotatory or Transverse Effect. By J. C. Beattie. (With 
a Plate.) 

(Read 17th June 1895.) 

Kundt # has shown that the transverse effect in iron, cobalt, and nickel is proportional 
to the magnetisation. Such an effect, where the magnetisation appears in the first power, 
we shall call a Hall effect. In applying the same method to bismuth, he found that no 
transverse effect was given by the thin plates of the electrolitically deposited metal used 
by him. That this absence of transverse effect is not characteristic of all bismuth so 
prepared has been shown experimentally. The question is, What relation, if any, exists 
between it and the magnetisation ? To settle this it is necessary to compare the 
transverse effect in any given plate with some other effect in the same plate whose 
relation to the magnetisation is known. Such an effect is the variation of resistance. 
GoLDHAMMERt has shown that this latter is proportional to the square of the magnetisa- 
tion. 

The current sent through the plate is called the primary. A thick copper wire was 
placed in the primary circuit, so that two fixed points in it could be inserted in the 
galvanometer circuit ; the reading thus obtained was used as a measure of the strength 
of the current. This brings in no error, since the measurements are throughout relative. 

By the rotatory or transverse effect is meant the ratio of half the galvanometer 
deflection (with proper sign), which is obtained when two equipotential or approximately 
equipotential points on opposite sides of the plate are inserted in the galvanometer 
circuit, to the strength of the primary current. The numerical value of this effect is 
denoted by E. 

To measure the resistance of the plate, two fixed points or lines in it were inserted in 
the galvanometer circuit ; the reading thus obtained divided by the strength of the 
primary current was taken to be proportional to the actual resistance of the plate. By 
this means it is rendered independent of the current strength. 

The resistance n + A n of a plate in a steady magnetic field, minus its resistance (n), 
when no field was there, — that is, An can be taken as proportional to the square of the 
magnetisation. 

If the transverse effect is a pure Hall, we shall have 

c 1N /A»=±E ... (1) 

Evidently this cannot hold for plates where E attains a maximum value : in such we 
must use a formula 

c 1 (Ara)* + c 2 (A»)2=±E . (2) 

In the following experiments a d'Arsonval galvanometer was used. The electro- 
magnet was ring-formed, and was wound with a wire capable of carrying a thirty ampere 

* Wiedemann's Annalen Neue Folge, Bd. 49, 1893. t Ibid., Bd. 36, 1889. 

VOL. XXXVIII. PART I. (NO. 7). 2 K 



242 MR J. C. BEATTIE ON THE 

current; the poles were circular surfaces 60 mm. in diameter and 18 mm. apart. By- 
inserting suitable resistances in the electro-magnet circuit any field required could be 
obtained. 

The field strength was measured by Verdet's method : as the strength does not come 
directly into the calculations it is given only approximately. The necessary measurements 
were made some weeks after the other experiments. 

The plates used were fixed on to strips of ebonite ; at both ends copper of the same 
breadth and thickness was soldered on, the ends of the copper dipped into pools of 
mercury. The two pools could be connected with the primary current and with the 
galvanometer simultaneously ; in this way the resistance of the plate perpendicular to the 
direction of the field was measured. It is to be noted that the resistance of the copper 
plates comes in, but as this does not vary in a magnetic field, An is not affected. 

To measure the transverse effect and the resistance along the lines of force two wires 
arranged as in fig. 1, were soldered on to the two middle points of the sides of the 
bismuth plate ; the ends of these wires dipped into four small mercury pools. 

The plates so arranged could be clamped in the field in either of two positions at 
right angles to one another. 

Three different positions of the plate with respect to the lines of force of the field 
were considered. 

Suppose the direction of the field to be parallel to the plane of the paper, and let this 
be our y-axis : let the 2-axis be drawn perpendicularly upwards, the ai-axis towards the 
reader. In the first position (a) the plate's surface was in the xz plane, and the primary 
current flowed in the z direction. In the second position (/3) the plate's surface was in 
the yz plane, and the primary current flowed in the direction z. The resistance 
measured in both these cases is the resistance perpendicular to the lines of force of the 
magnetic field. 

In the third position (y) the plate's surface was in the yz plane, and the primary 
current flowed in the direction y. With this arrangement the resistance along the lines 
of force could be measured by sending the primary current in at (1) or (2), while at the 
same time (3) and (4) were joined to the galvanometer. 

It was found, however, that this latter arrangement was not very suitable, and in the 
greater number of cases another method (fig. 8) was used. The plate was fixed on to 
another piece of ebonite. Along the sides thick copper wires were soldered throughout the 
whole length ; these served for the primary current. Two other wires were soldered along 
the length of the plate, but were not in direct contact with the other two : one end of 
each of these was joined to the galvanometer. 

The transverse effect was measured with the plate in position a. 

No attempt was made to keep the temperature of the plate constant by using liquids ; 
the temperatures given are the approximate temperatures of the room during the time of 
the experiment. Between the different experiments, however, a pause was made to allow 
the plate to cool. 



RELATION BETWEEN THE VARIATION OF RESISTANCE IN BISMUTH. 



243 



It may be stated that for weak fields the method here given for measuring the resist- 
ance is not suitable. For such the Wheatstone bridge or the differential galvanometer 
would give good results in less time. 

Of the different plates used, only one was known to be perfectly pure. With it the 
following results were obtained : — 



Length, . 
Breadth, . 
Thickness, 



16-75 | 

7-2 -: 



Temp. 10° C. w='9521 



c,= -E 



J An 



Field in 
cgs. Units. 


Transverse 
Effect. 


a 

An 


jAn 


An 


J An 


y 

An 


JAn 


a 


P 


y 


8,500 


-•2311 


•2949 


•5420 


•3144 


•5648 


•1489 


•3858 


-•42 


-•41 


-•60 


9,500 


- -2455 


•3292 


•5738 


•3556 


•5963 


•1622 


•4027 


-•42 


-•41 


-•60 


11,700 


- -2627 


•4001 


•6325 


•4333 


•6582 


•1780 


•4219 


-•41 


-•40 


-•62 


12,840 


- -2708 


•4552 


•6747 


•4717 


•6768 


•2066 


•4545 


-•40 


-•40 


-•59 


14,170 


- -2974 


•4815 


•6932 


•5258 


•7251 


•2357 


•4855 


-•42 


-•40 


-•61 


15,600 


- -3071 


•5881 


•7669 


■5684 


•7539 


•2500 


•5000 


-•40 


-•40 


-•61 


17,800 


- -3271 


•6281 


•7926 


•6252 


•7907 


•2704 


•5389 


-•41 


-•41 


-•60 



The relation between the transverse effect and the variation of resistance is a simple 
one. The constants obtained for the positions a and /3 are the same : that for y is 
different ; but it is to be remembered that the results given above depend upon the form 
of the plate and upon the external resistance inserted in the galvanometer circuit, which 
differed in position y from that in a and ft. To eliminate the various disturbing effects 

the quantity J should be used in equation (1) instead of ^ An. 

The two next plates were made from different supplies of commercial bismuth. 
In them the numerical value of the transverse effect did not reach a maximum with the 
fields at disposal. 

In Plate II. the simple relation (1) no longer applies ; the equation (2) was therefore 
used. 

The average values of the constants c x and c 2 were obtained by solving the equations 
obtained from combining the results for each field with those for every other ; the two 
results immediately before and after were in each case rejected : — that is, with twelve 
different field strengths, 1 . . . 12, we get eleven equations by combining result 6 say 
with all others, but of these those derived from 5 and 7 were rejected. 



244 



MR J. C. BEATTIE ON THE 



Plate II. 



Length, 
Breadth, 
Thickness, 



16-5 
8-0 



irl 



mm. 



n=-83 
Temp. 9° C. 

c 1 (A»)i + c 2 (Aw)5= -E. 



Field 
in cgs. 
Units. 


Trans. 
Effect. 


a 
An 


J An 


An J A 7i 


y 

An J A n 


a 


c 1 c 2 


y 


1,170 


- 4087 


•0110 


•1049 




... 








1,840 


-•1270 


•0150 


•1279 








... 




2,520 


- -2220 


•0460 


•2145 






-1-04 +'30 






3,180 


- 3249 


•1041 


•3229 


•1018 3190 




-1-04 +-30 


-1-05 +-32 




5,030 


- 3840 


•1499 


•3872 




•2865 -5352 


-104 +-30 






8,500 


- 5147 


•2945 


•5427 




•5696 -7540 


-1-04 +-31 




-•74 +1-2 


9,500 


- 5264 


•3130 


•5594 






-104 +-30 






11,740 


- 5679 


•3756 


6129 


•3805 6163 


•7577 -8704 


-104 +-30 


-1-04 +30 


-•74 +1-1 


12,840 


- 6075 


•4573 


6761 






-1-04 +-30 






14,200 


-•6181 


•4919 


7013 


•4820 -6944 




-1-04 +-30 


-1-04 +-28 




15,600 


- 6302 


•5300 


7215 






-1-04 +"30 






17,780 


- -6600 


•6081 


7798 


•6023 -7716 


1-0062 10031 


-1-04 +-30 




-•75 +1-2 


- 










Average, 


-104 +-31 


-1-04 +31 


-•75 +1-2 



In Plate IX. the relation between the transverse effect arid the resistance variation 
perpendicular to the field was alone considered. Owing to the size of the plate the 
arrangement — e — was somewhat different. The plate was fixed on to stiff cardboard, 
the transverse electrodes were soldered to the middle points of the sides, the primary 
electrodes to the middle points of the ends. The plate was then placed with its surface 
perpendicular to the lines of magnetic induction and kept clamped in this position. 

We see that in these two plates we have not to deal with a pure Hall effect only ; 
we have in addition a second effect, which is positive and proportional to ( Anf that is to 
the magnetisation cubed. 

The results for Plate IX. and for all the plates showing two effects can be 

represented graphically ; the resistance variation is measured along the horizontal axis. 

-E . . 

Along the perpendicular axis the values of — are laid down ; the connecting curve is 

a straight line, which, when produced to meet the perpendicular axis, gives the value 
of Cj. To obtain such a curve for any plate, at least two direct measurements of the 



RELATION BETWEEN THE VARIATION OF RESISTANCE IN BISMUTH. 



245 



Plate IX. 



Length, 

Breadth, 

Thickness, 



60-1 
30-3 
3-1785 



n = 1-4052 
Temp. 14° C. 



Field. 



1,340 

3,350 

5,030 

6,700 

8,800 

11,300 

14,750 

17,780 



Trans. Effect. 


- 


0469 


- 


0943 


- 


1202 


- 


1505 


- 


1700 


- 


1879 


- 


1999 




2072 



An 



J An 



•0240 
•1020 
•1760 
•2975 
•4190 
•5823 
■7735 
•9870 



•1549 
•3194 
•4195 
•5454 
•6473 
•7631 
■8795 
•9985 



Average 



Cj(A?i)2 + c. 2 (An) : i = E. 

C, C 



•30 


+ •097 


•30 


+ •107 


•30 


+ •098 


•30 


+ •101 


•30 


+ •101 


•30 


+ •100 


•30 


+ •098 


•30 


+ •100 



transverse effect and of the variation of resistance must be made ; with these we obtain 
two points on our line. For any other variation of resistance value we can then find 
the transverse effect and resolve it into a pure Hall effect and this second effect. 

Evidently the graphic method could also be applied to determine c x and c 2 in the 
first instance, instead of the method of equations used in this paper. 

The next plates used were two in which the transverse effect attains a maximum 
numerical value. 

In these two plates also, which were made from the same two supplies of bismuth, 
we have two effects. 

Finally, two plates were considered in which the second effect is so great as to 
completely mask the true Hall, so that even with the low fields at disposal the 
transverse effect changes sign. 

The results of experiments with Plates Ib. and VI. by a different method : — viz., 
that described in paper, " On Hall Effect and some Eelated Effects in Bismuth," were 
qualitatively the same. For Ib. the values of c x and c 2 were respectively d =' — "45 
c 2 = +4*4 and for VI. c x = -'238 c. 2 = +3-3. 

We may sum up the results so far obtained by saying that in the pure bismuth 
plate the Hall effect alone is present : it is proportional to ( A nf and is negative in sign. 
In the other plates the transverse effect is composed of two effects, the pure Hall and 
another, positive in sign and proportional to (Aw)-. In different plates this effect 



24G 



MR J. C. BEATTIE ON THE 



appears in different magnitude ; in some it is relatively so small, compared to the 
Hall effect, that it does not, with the fields at disposal, cause the total effect to 
decrease numerically. In others, again, it produces this ; and in a third class it 



Plate VIII. 



Length, . 
Breadth, 
Thickness, 



24-0 | 
12-0 mm. 

1-1365 ) 



n = 1-3967 
Temp. 15° C. 

c 1 (Ari)i + c 2 (An)l = -E. 



Field. 


Trans. Effect. 


c 

An 




An 


J~An 


y 

c i H 


S 

c i 


C 2 


1,340 


-•10221 


•0320 


•1780 


... 




... 


... 


... 


... 


3,350 


-•19552 


•1253 


•3539 


•0452 


•2126 


... 


... 


... 


... 


5,030 


•23712 


•2029 


•4500 


•0712 


•2668 


-•58 


+ •27 


-•96 


1-2 


6,700 


- -28526 


•3244 


•5697 


•1135 


•3369 


-•58 


+ •25 


-•96 


11 


11,300 


- -33459 


•6067 


•7789 


•1943 


•4409 


-•58 


+ •25 


-•96 


1-1 


12,840 


- -33879 


•7199 


•8489 






-•58 


+ •25 


... 




14,750 


-•33456 


•7803 


•8833 


•2416 


•4914 


-•58 


+ •26 


-•96 


1-2 


17,780 


-•3147 


•9709 


•9853 


•2699 


•5195 


-•57 


+ •26 


-•98 


1-4 












Average 


-•58 


+ •26 


-•97 


1-2 



Plate Ia. — Arrangement e. 



Length, 

Breadth, 

Thickness, 



50 

28-25 : nun 
1-305J 



» I 



n = 1-056 
Temp. 15° C. 











c^AnY' + c^AnYt-- 


= -E. 


Field. 


Trans. Effect. 


An 


JAn 


<h 


C 2 


8,500 


- -2902 


•2529 


•5029 


... 


... 


11,740 


- -2900 


•3262 


•5712 


-•83 


+ •98 


12,840 


-•2898 


•3274 


•5722 


-•81 


+ •94 


14,170 


-•2739 


•4121 


•6419 


-•83 


+ •95 


15,600 


- -2621 


•4321 


•6573 


-•80 


+ •99 


17,780 


- -2503 


•4816 


•6939 


-•82 


+ •95 








Average 


-•82 


+ •96 



RELATION BETWEEN THE VARIATION OF RESISTANCE IN BISMUTH. 247 



Length, 
Breadth, 
Thickness, 



Plate XII. 
24-0 

11-75 !> - 
•95 



n = 2-08 
Temp. 14° C. 

^(A^+c^Aji)^ ±E. 



Field. 


Trans. Effect. 


a 

An J A n 


A n 


/3 

J 'An 


a 


C 2 


i8 


C 2 


1,340 


- -0475 


•0139 


•1179 




... 


... 




... 




2,680 


- -07266 


0373 


•1931 




... 


... 




... 




3,350 


- '08131 


•0517 


•2274 


•0382 


•1955 


-•41 


+ 1-2 


... 




5,030 


- -0976 


•0776 


•2786 


•0559 


•2383 


-•41 


1-2 


-•50 


+ 2-2 


6,700 


- -08922 


1393 


•3732 


•0900 


•3000 


-•42 


1-3 


-•50 


+ 2-3 


8,820 


- -07009 


•1906 


•4366 


•1282 


•3580 


-•41 


1-3 


-•50 


2-4 


14,750 


- -00519 


•3318 


•5760 






-•43 


1-2 


... 




17,780 


+ -04702 


•3816 


•6177 


•2322 


•4819 


-•42 


1-3 


-•50 


2-4 












Average, 


-•42 


+ 1-3 


-•50 


+ 2-5 



Length, 

Breadth, 

Thickness, 



Plate X. 

38-8 | 
20-5 |>mm. 
W12 ) 



1-8041 
Temp. 9° C. 











(\ JAn + c 2 (An)"* = 


±E. 


Field. 


Trans. Effect. 


< 

Am, 


J An 


c i 


C 2 


1,840 


•01708 


•0148 


•1217 






2,520 


- 01944 


•0221 


•1487 






3,180 


- -01974 


•0400 


•2000 


-•16 


+ 1-7 


4,100 


- -01784 


•0455 


•2133 


-•16 


1-8 


8,500 


+ •01361 


•1300 


•3606 


-•17 


1-6 


10,800 


+ -02650 


•1502 


•5875 


-•15 


1-6 


12,840 


+ -06014 


•1830 


•4278 


-15 


1-7 


14,170 


+ -07676 


•1977 


•4448 


-•16 


1-7 


15,600 


+ •09602 


•2033 


•4575 


-•16 


1-8 


17,780 


+ •12024 


•2215 


■4707 


-•16 


1-8 



248 MR J. C. BEATTIE ON THE 

is present to such an extent that in the end it gives its sign to the total transverse 
effect. 

This second effect is not to be confounded with the thermo-magnetic effect observed 
by Ettingshausen and Nernst : the latter is evidently proportional to ( A nf and 
positive in sign. 

The anomalous behaviour of the transverse effect in bismuth — which is hidden, if the 
effect be represented in terms of the rotatory co-efficient R — has also been observed by 
Ettingshausen and Nernst.* They found that in a specimen of pure bismuth, E 
obtained a maximum value, — that is, both effects may appear in pure bismuth. Again, 
Ettingshausen t has shown that, in an alloy of tin and bismuth, the transverse effect 
changes sign. At high fields, when little tin is present : at lower, when more tin is added 
until when the alloy contains 6 % tin, 94 °/ o bismuth, the positive sign alone is present. 
The explanation lies in the presence of this second effect, which increases relatively to 
the pure Hall effect as the proportion of tin to bismuth increases. 

It is interesting to note that the relation between transverse effect and resistance 
variation holds, no matter what the percentage increase of resistance is, or how much the 
transverse effects expressed in terms of R vary in the different plates. 

So far, the transverse effect has only been observed when the electrodes are at the 
middle points of the sides. A number of experiments were next made with these 
electrodes at different parts, while still kept opposite each other. In Plate Ia. the 
numerical value of the transverse effect was found to have a maximum value with the 
electrodes in the middle ; for other positions it was less. The greater the distance from 
the middle points, the greater was the decrease. Next, the same plate was cut along the 
middle line for about half its length. The electrodes were fixed at a b, c d, e f, 
respectively, fig. 2, and the effect was found to be greatest at a b, less at e^and c d. 
Finally, another slit was made along the middle line, and the electrodes were placed at 
/'and g, fig. 3. The effect was qualitatively the same, but quantitatively less. 

The question to settle now is, Whether this decrease is due to a decrease in the pure 

Hall effect ? in the second effect ? or in both ? If we take the ratio for any one plate, 

n 

we get a number which may be looked on as characteristic of that plate ; it is 

independent of its dimensions, and depends only on its properties. If these are the 

same throughout — which we assume to be the case — and if we neglect the slight 

disturbances due to the fact that the temperature is not absolutely constant throughout 

the experiments, this number may be used to divide the transverse effect into its two 

constituents, and to give the relative values of these for any one plate, no matter how it 

is modified in size or shape. That is, we now apply the equation 

o(4-? + <ir>-± E • • < 3 >- 

* tiitz. bericht der hods. Akad. der JFissenschaft, Wien, 1886. 
t Sitz. bericht der kais. Akad., Wien, 1887. 



RELATION BETWEEN THE VARIATION OF RESISTANCE IN BISMUTH. 249 

When this is done, we find that the decrease in the transverse effect, when the plate has 
the form fig. 3, is due to a decrease in both effects. Similarly, the decrease, as we move 
towards the ends, is also due to a decrease in both. 

Another plate, VIIIa, was used next. The transverse electrodes were first placed in 
the middle, then at points 2 mm. from the ends, the transverse effect in the second posi- 
tion was the smaller. The results, treated as in I a, showed that the decrease was again 
due to a decrease in both effects. 



Plate VIIIa. 



Length, . 
Breadth, . 
Thickness, 



44-0 
21-0 
1-05 



Temp. 15° C. 



(¥}+<&--* 



Field. 


Trans. Effect 
with Elect. 
in Middle. 


Trans. Effect 
with Elect, 
near. Ends. 


Aw, 
n 


v/An 
n 


Electrodes in 
Middle. 

°1 C 2 


Electrodes near 
Ends. 


3,350 


-•1616 


- 1463 


•0616 


•2482 


-•69 +-74 


- -63 + -68 


6,700 


-•2371 


-•2107 


1716 


•4142 


- -67 + -72 


-•62 +-64 


11,300 


- -2612 


- -2348 


•3091 


•5559 


- -68 + -70 


- -63 + -68 


17,780 


- -2377 


- -2066 


•5009 


•7077 







In Plate X. the electrodes were first soldered on to middle points of the sides, then to 
points 4 mm. from the end ; the variation, however, was so small that no conclusion could 
be drawn as to its cause. This plate was also slit along the middle line, so that it had 
the form given in fig. 3, the results were qualitatively the same, but showed a decrease 
in E. This same plate, after being used for some time, showed a change in the field 
strength necessary to make the effect vanish. A higher field became necessary. The change 
was very small, and the application of equation 3 showed that the pure Hall effect had 
increased, while the second effect remained practically constant. 

In a former paper it was shown that, in plates for which the transverse effect changes 
sign, the field strength at which the effect vanishes is raised when the plate is hammered 
or filed. To find what change in the pure Hall or in the second effect is concerned in 
this, the results obtained with Plate Ib were examined ; and it would appear that the 
pure Hall effect varies, while the second remains practically constant. 

VOL. XXXVIII. PART I. (NO. 7). 2 L 



250 



MR J. C. BEATTIE ON THE 



Plate Ib. 



Length, 

Breadth, 

Thickness, 



44-7 
208 
1-2235 



mm. 



^•♦<*/£>-« 



Field (about). 


Trans. Effect. 


n 


v u 


e i 


C 2 


3,864 


- -07693 


•0408 


•2019 






8,694 


- -02957 


1002 


•3165 


-•58 


+ 4-8 


16,284 


+ •15039 


•1828 


•4276 


-•57 


+ 5-1 


19,320 


+ -21259 


■2203 


•4639 


-57 


+ 4-7 

1 



The plate was next hammered and, approximately, the same field strengths used. The 
results were now — 



ca 



(£*\ + J*S)i-± 



X V n 



:E. 



Field. 


Trans. Effect. 


A n/n J A njn 


c i 


C 2 




As in last. 


-•0126 


As in last. 






Do. 


- -05166 


Do. 


-•73 


+ 5-7 




Do. 


+ -11249 


Do. 


-•72 


+ 5-3 




Do. 


+ -19027 


Do. 


-73 


+ 5-2 





Finally, the plate was filed down, its thickness being reduced to 665 mm. which, when 
the variation of resistance is taken into account, gives us 

c x = - -76 c 2 = +5-4. 



Field. 


Trans. Effect. 


<h 


C 2 


3,864 


- -21699 


... 


... 


8,694 


-13521 


-1-52 


10-9 


16,284 


+17013 


-1-50 


10-4 



The same results were obtained with Plate IX. It was first used when its thickness 
was 318 mm. The constants for this were — 

(.-!= --18 c 2 = +-085. 



RELATION BETWEEN THE VARIATION OF RESISTANCE IN BISMUTH. 251 

Next it was filed down till a thickness 1 "56 mm. was obtained. The constants were now — 

c 1 = --42 c 2 = + 171. 

That is, the pure Hall effect has slightly increased ; the second effect has remained constant. 

From the above we conclude that when a plate is slit along the middle line, as Ia, the 
transverse effect changes in numerical value, but not in sign ; the fact also that the effect 
decreases, but qualitatively does not change as we pass from the middle towards the ends, 
admits of a similar explanation. For, suppose we have a plate with electrodes (transverse) 
at a and h (fig. 4), the rotatory effect may be represented as in the figure. When the 
slits are made, several lines are interrupted (fig. 5) ; and when we approach the ends, the 
complete number of lines is given only on one side of the connecting line. The single 
safe conclusion to be drawn seems to be that the state of the plate, when it gives a 
transverse effect, is symmetric with respect to the middle line of its length. 

The causes of the pure Hall effect and of the second effect seem to be very intimately 
connected. Only by hammering or by filing a plate does it seem possible to vary one 
without varying the other. 

Evidently the relations obtained between the transverse effect and the resistance 

variation for the various plates do not allow us to compare the values of the constants 

A fi 

in different plates, even when we use ; for this latter is a variable standard, depend- 

n 

ing on the plate and the temperature. 












Vol. XXXVI 



I Beattie on the Relation between the Variation of Resistance and the Transverse Effect in Bismuth. 



n 



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Page 
VIII. On the Comparative Histology and Physiology of the Spleen. By A. J. Whiting, M.D. 

(With Three Plates), . . . . . . . .253 

(Issued separately, December 9th, 1895.) 

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( 253) 



VIII. — On the Comparative Histology and Physiology of the Spleen. 
By A. J. Whiting, M.D.* (With Three Plates.) 

(Read 10th January 1893.) 



CONTENTS. 



PART I. 

Ox the Comparative Histology of the Spleen. 

Chapter I. 

PAGE 

The Supporting Framework of the Spleen, . . . 254 

The Tunica Serosa — 

in the Skate, Ling, and Cod, 255 

in the Frog, Tortoise, Grass Snake, .... 255 
in Birds and Mammals, 255 

The Tunica Propria, the Trabeculaa, and the Hilar Sheath — 

in the Skate 255 

in the Ling, 255 

in the Frog, 256 

in the Tortoise, 256 

in the Grass Snake, 256 

in the Hawk, 257 

in the Rook, 257 

in the Pig, 257 

in the Ox, 257 

in the Sheep, 258 

in the Dog, 258 

in the Cat 258 

in the Narwhal, 258 

in the Porpoise, 258 

in the Rabbit, Rat, and Guinea-pig, .... 259 

in the Hedgehog 259 

in Man, 259 

Summary, 260 



Chapter II. 

The Adenoid Sheath of the Splenic Arteries and the Splenic 

Follicles, 260 

The Adenoid Sheath — 

in the Cod, . 262 

in the Skate 262 

in the Frog 262 

in the Tortoise, 262 

in the Grass Snake, 263 

The Splenic Follicles — 

in the Rook, . . 263 

in the Ox, 263 

in the Sheep, 264 

in the Pig, 264 

in the Cat, m 264 

in the Dog 265 

in the Porpoise 265 



The Splenic Follicles {continued) — 

in the Narwhal, 265 

in the Rabbit, . 266 

in the Rat, . 266 

in the Guinea-pig, ....... 266 

in the Hedgehog, 267 

in Man 267 

Summary, ......... 268 

Chapter III. 
The Ellipsoidal Sheath of the Splenic Arteries and the 

Splenic Ellipsoids, 269 

in the Skate, 269 

in the Cod, 269 

in the Frog, 269 

in the Tortoise, 270 

in the Grass Snake, 270 

in the Hawk, 270 

in the Rook, 270 

in the Pigeon 271 

in the Ox, 271 

in the Sheep, 271 

in the Pig, 272 

in the Dog, 272 

in the Cat, 272 

in the Porpoise and Narwhal, 273 

in the Rabbit, Eat, Mouse, and Guinea-pig, . . 273 

in the Hedgehog 273 

in Man 273 

Commentary, ......... 273 

Summary, 274 

Chapter IV. 

The Splenic Pulp, . . .275 

in the Dog, 275 

in the Skate 276 

in the Cod and Ling, 276 

in the Frog, 277 

in the Tortoise, 278 

in the Grass Snake, 279 



. 279 

. 279 

. 279 

. 281 

. 282 

. 284 

. 285 

in the Rabbit, 285 

* This paper consists of the principal part of a thesis presented to the University of Edinburgh in 1892, for the 
degree of Doctor of Medicine, which was awarded a gold medal and an equal share of the Goodsir Prize. 

VOL. XXXVIII. PART II. (NO. 8). 2 M 



in the Hawk and Pigeon, . 

in the Rook, 

in the Pig, Sheep, and Ox, 

in the Dog, 

in the Cat, 

in the Porpoise, 

in the Narwhal, 



254 



DR A. J. WHITING ON THE 



PAGE 

The Splenic Fulp {continued) — 

in the Rat, 2S6 

in the Mouse, 287 

in the Guinea-pig, 288 

in the Hedgehog, 288 

in Man 289 

Commentary, 293 

Summary 293 

PART II. 

On tjie Physiology of the Spleen and Blood Formation. 

Chapter V. 

Historical Epitome, 296 

Description of Leucocythremic Spleen, . . . . 298 



PAGE 

298 
301 
302 
309 
310 



On Artificial Anaemia in Dogs, 

Description of Spleens of three Anaemic Dogs, . 

Two Experiments on Anaemia in Dogs, 

Results of Experiments, 

Summary of Effects of Haemorrhage, 

On Artificial Anaemia in the Rabbit and Description of 

Spleen of Anaemic Rabbit, 310 

PART III. 

Methods— Bibliography — Description of Figures. 

Chapter VI. 

Methods, 311 

Bibliography, 314 

Description of Figures 316 



PAET I. 

On the Comparative Histology of the Spleen. 



Chapter I. 
The Supporting Frameivork of the Spleen. 

The following general description of the capsule, trabeculse, and sheaths of the 
splenic vessels is based on the examination of the spleen of the Kitten. 

Tlie Tunica serosa consists of a single layer of somewhat thick endothelial cells, 
which is continuous with the peritoneal lining of the body cavity, and in addition of a 
thin layer of very finely fibrillated connective tissue that lies immediately subjacent to 
the endothelial layer. 

Tlie Tunica propria differs from a true capsule in that it blends along its whole 
under surface with the splenic parenchyma, from which it cannot be detached without 
tearing the splenic substance. 

It is composed of two layers, one consisting of ordinary connective tissue and the other 
of muscular tissue. The more superficial layer is formed of interlacing bundles of white 
fibrous tissue, between which are a few lymphoid cells, and of many strands of elastic 
tissue, which, when stained with picrocarmine, appear as highly refractile yellow bands 
or dots according as they are seen longitudinally or in transverse section. About mid- 
way in the thickness of the tunica propria spindle-shaped muscle fibre cells begin to 
appear. They increase in number until, at the inner fourth of the capsule, they form a 
continuous layer principally directed transversely to the long axis of the spleen. Above 
the circular muscular layer, as well as below it, there are a few longitudinally arranged 
muscle fibre cells. 

From the circular muscular layer of the capsule the trabeculse spring as gently curved 
bands, and are themselves composed of non-striped muscle. 

As the artery enters the spleen, along with the nerves, at the hilus, it receives a 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 255 

somewhat thick sheath from the tunica propria, which is therefore composed internally 
of white fibrous tissue and externally of unstriped muscle. This investment may be 
called the capsular or hilar sheath. The external layer is almost immediately rein- 
forced by the junction of the muscular trabeculse. The fibrous tissue next the outer 
wall of the artery is finer, looser, and contains more lymphoid cells than that near the 
external muscular layer, and it is apparently derived, in part at least, from the sub- 
endothelial connective tissue of the tunica serosa, which is more abundant in the 
neighbourhood of the hilus. 

The splenic vein, while accompanied by the artery and nerves near the hilus and 
internal to it, is invested by a somewhat thin covering of fibro-muscular tissue derived 
from the hilar sheath. In the interior of the spleen, when separate from the artery, the 
vein runs within or at the side of a trabecula. The veins are conducted to the hilar 
sheath by the trabecula?, where they are surrounded by dense muscular or fibro-muscular 
tissue without the intervention of a looser fibrous laj 7 er. 

The Tunica Serosa. 

The Tunica serosa in all animals consists of a single layer of cells that individually 
vary in shape in different animals. The endothelial cells covering the spleen of the Skate 
are columnar in shape. In the Ling and Cod they are low columnar or cubical. In the 
Frog and Newt they are somewhat shorter than in the bony fish, and approach a pointed 
oval shape. In the Tortoise they are a little lower than in the Amphibia. In the Grass 
Snake they are still more flattened than in the tortoise, but are at the same time 
somewhat thick. In adult Birds and Mammals they are squamous, but in foetal 
mammals they are cubical, and during the first few weeks of extra-uterine life they are 
thick, but flattened like those of the Amphibia and Ophidia. 

Thus the cells of the tunica serosa, as the scale is ascended from fishes to mammals, 
become gradually more flattened out. 

The Tunica Propria, the Trabecule, and the Hilar Sheath. 

In the Skate the tunica propria is principally composed of white fibrous tissue 
arranged in large loosely interwoven bundles, between which there are a few lymphoid 
cells. In the deeper portion of the capsule there are some spindle-shaped muscle fibre 
cells which do not form a distinct layer. In the substance of the capsule, near the 
parenchyma, there are a few narrow venous sinuses. There are no true trabeculse. 
In addition to the capsule, the only representative of a supporting framework is the 
loose fibrous tissue, derived from the tunica propria, that accompanies the vessels 
through the hilus. 

In the Ling the tunica propria appears to be composed of three layers. The outermost 
layer consists of loosely arranged spindle-shaped cells, that stain deeply with hsema- 
toxylin and closely resemble connective tissue corpuscles. The intermediate layer is 



256 , DE A. J. WHITING ON THE 

relatively thick, and formed of interlacing bundles of white fibrous tissue containing 
many lymphoid cells and many large blood-vessels and nerves. The innermost layer is 
denser and thinner than the others (it is about one-fifth the thickness of the inter- 
mediate layer), and is composed of unstriped muscle fibre cells that are rendered con- 
spicuous by staining deep-pink with cosine. 

Joining the under surface of the lower muscular layer are delicate, open, fibrous strands 
that consist mainly of spindle cells, many of which are muscular. These strands are con- 
tinuous with others that form a nearly regular meshwork, and which divide the paren- 
chyma into a series of polygonal areas. In the middle of each area is an arteriole or a 
capillary blood-vessel enveloped in its special sheath. 

The hilar sheath is very strongly developed in the teleostean spleen ; its peripheral 
portion is distinctly muscular. The fibrous strands that bound the polygonal areas are 
apparently derived from this outer portion of the hilar sheath. 

In the Frog the tunica propria consists of white fibrous tissue arranged more or less 
distinctly in bundles. Scattered throughout its substance are spindle-shaped fibre cells, 
which are almost certainly muscular. These are specially noticeable immediately 
under the tunica serosa and also adjoining the parenchyma, as in the capsule of the 
cod's spleen. Imbedded within the substance of the tunica propria are numerous very 
large venous sinuses which are connected by somewhat large branches with the 
venous sinuses of the pulp. Around the capsular blood-sinuses the spindle-shaped 
fibre cells form a comparatively thick layer which stains pink with eosine, and is 
undoubtedly muscular. There are no true trabeculse. The only representative of the 
supporting framework in the interior of the spleen is a relatively small amount of 
fibrous tissue forming a sheath for the blood-vessels. 

In the Tortoise the tunica propria consists of two layers, the outer composed of 
white fibrous tissue staining faintly blue with hsematoxylin, and the inner composed of 
unstriped muscle staining deeply with eosine and picric acid. The outer looser layer 
contains a few large, clear, faintly stained lymphoid cells ; in the inner layer immedi- 
ately subjacent to the outer layer there are venous sinuses somewhat larger than those 
in the frog, and like them surrounded by muscle. There are no true trabeculse. The 
arteries run in a thick fibrous sheath, which externally is strongly muscular, corre- 
sponding with the inner layer of the capsule. Immediately surrounding the artery 
is a layer of loose areolar tissue containing a few clear lymphoid cells corresponding, 
therefore, with the superficial layer of the capsule. 

In the Grass Snake the tunica propria is composed of dense fibro-muscular tissue. 
It consists chiefly of white fibrous tissue towards the surface, while deeper it is almost 
entirely muscular. Within the muscular portion large venous sinuses are very numerous, 
as in the skate, frog and tortoise. Where the muscular portion joins the parenchyma, 
its fibres separate so as to form elongated meshes in which are rows of lymphoid cells. 
Four broad trabeculas-like processes, somewhat wedge-shaped, composed of tissue 
resembling that of the deeper portion of the tunica propria, but more loosely arranged, 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 257 

pass from the under surface of the capsule into the substance of the spleen to join a large 
fibrous core. Both processes and core contain wide venous sinuses which communicate 
with each other and with those of the capsule. This supporting framework appears to 
represent a strongly developed hilar sheath rather than a true trabecular system. 

In the Hawk the tunica propria is composed of a loose network of white fibrous 
tissue, in the meshes of which are a few lymphoid cells, and contains, irregularly 
interspersed, many spindle-shaped muscle fibre cells. There are no trabecule. There 
is a somewhat strongly developed hilar sheath, a considerable proportion of which 
consists of non-striped muscle. 

In the Rook the tunica propria may be divided into three layers ; first, an outer 
thin layer of white fibrous tissue, containing many elastic fibres ; second, an inter- 
mediate thin muscular layer, the fibres of which run longitudinally ; and third, a 
transverse muscular layer, four or five times thicker than either of the other layers. 
Between the two muscular layers is a row of lymphoid cells. There are no true 
trabecular. The arteries and veins are invested by a thick hilar sheath, the outer part 
of which is purely muscular. 

In the spleen of the Pig the tunica propria is composed almost entirely of non- 
striped muscle. There is externally a thin layer of white fibrous tissue, and the rest is 
muscle, which is mainly arranged in two layers — an outer layer of transverse fibres 
and an inner thicker layer of longitudinal bundles ; but there are also many strands 
arranged obliquely. From the deeper longitudinal layer massive muscular trabecular 
arise, which, passing inwards, anastomose to form a very coarse network. From the 
periphery of these large trabecular, and from the under surface of the capsule between 
their points of attachment, there are given off a few microscopic trabecular, which form a 
secondary network within the meshes of the larger network. Some of these are attached 
to the vascular sheaths, others end in the pulp apparently by becoming connected 
with its reticulum. The venous trunks, before they join the arteries, are intimately 
connected with the larger or primary trabeculse. The hilar sheath has a very strongly 
developed muscular layer which unites with the trabecular. A noticeable peculiarity 
in this spleen is that the arteries divide into smaller branches within the hilar sheath. 

In the Ox the arrangement of the tunica propria resembles closely that in the pig. 
The layer of loose connective tissue under the tunica serosa is thicker, and contains 
more connective tissue corpuscles. The deeper muscular portion, as in the pig, is 
composed mainly of two layers, a superficial layer transverse and relatively thin, and 
a deep layer longitudinal and very thick ; but oblique fibres are by no means so 
numerous as in the pig. Springing from the deeper layer, large muscular trabecular 
pass into the parenchyma, and from them, as well as from the under surface of the 
capsule, numerous microscopic trabecular arise and scatter themselves throughout the 
pulp, and cease only around the termination of the arteries. These microscopic 
trabecular are much more numerous and much stronger than in the pig's spleen. A strong 
hilar sheath envelopes the blood-vessels and nerves, and its outer portion is composed 



•2.')S DR A. J. WHITING ON THE 

of a remarkably thick muscular layer. Conspicuous within the hilar sheath are numerous 
large nerve trunks. Sometimes a nerve may be seen to run alongside of or within a 
trabecula, unaccompanied by any vessel. 

In the spleen of the Sheep the general arrangement is similar to that in the pig and 
ox, but the muscular bundles are usually more loosely arranged than in them, and the 
microscopic trabeculse are less strongly developed than in the ox, but more strongly than 
in the pig. 

In the Dog the tunica propria is composed of two nearly equal portions. The outer 
half consists of interlacing bundles of white fibrous tissue containing numerous con- 
nective tissue corpuscles and elastic fibres with a few lymphoid cells. The inner' half 
is composed of unstriped muscle mostly arranged in two layers, the outer of which is 
transverse and the inner longitudinal. In the spleen of the puppy muscular fibre cells 
are sparse, and occur only in the deeper part of the capsule. The trabeculse, which 
are almost entirely muscular, are both numerous and large, but in the puppy they are 
much less numerous. The majority of them are tunnelled by veins. The artery is 
immediately surrounded by a somewhat thick layer of fine connective tissue, outside 
which is a strong cylindrical sheath of muscle. 

In the Cat the greater proportion of the tunica propria consists of unstriped 
muscle, externally there is merely a thin layer of white fibrous tissue. Most of the 
muscle fibres are arranged transversely, so as to form a circular coat, but above as well 
as below this there are a few strands of longitudinally arranged fibres. The trabeculse, 
which are strongly developed, spring from the thick circular layer of the capsule, and 
are composed almost entirely of muscle. The hilar sheath is also well developed (Plate I. 
fig. 1). Its outer muscular layer is the thicker. Shortly after the artery has passed 
through the hilus, its loose connective tissue sheath, derived from the inner layer of the 
hilar sheath, contains a few lymphoid cells. In the newly-born kitten the capsule has 
no distinct muscular layer, and the trabeculse are small and sparse. 

In the Narwhal the tunica propria is composed of two layers ; a superficial thicker 
layer consisting of wavy bundles of white fibrous tissue with many elastic fibres 
scattered at intervals, and a deeper thinner layer consisting chiefly of non-striped 
muscle. There are no true trabeculse. Usually the veins are immediately surrounded 
by the parenchyma, but occasionally there may be seen a few strands of unstriped 
muscle supporting the larger veins. The vessels are accompanied into the interior of 
the organ by a large amount of fibrous tissue, containing in its meshes numerous 
lymphoid cells. Towards the periphery of the hilar sheath, unstriped muscle fibre cells 
may generally be observed, among which there may sometimes be seen triradiate muscle 
fibre cells similar to those found in the urinary bladder of Amphibia. 

In the Porpoise the tunica propria is much thicker on the side that corresponds 
with the concave or hilar surface of the spleen. On the convex surface it may be 
roughly divided into two layers : a superficial layer composed of white fibrous tissue, and 
a deeper layer composed almost entirely of unstriped muscle. On the hilar surface it 



COMPAKATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN". 259 

is thickened by the addition of an intermediate layer, composed of areolar tissue, which 
contains many arteries and many relatively large thin-walled veins. The latter feature 
reminds one of the intracapsular venous sinuses in cartilaginous fishes, in the Amphibia, 
in the Chelonia, and in the Ophidia. This intermediate layer also contains fat cells and 
numerous strands of unstriped muscular fibre. The trabecular system is but slightly 
developed. The trabeculse, which are apparently derived chiefly from the vascular 
sheaths, are in the form of flattened bands of long muscle fibres, each band so loosely 
arranged that elongated meshes result, in which numerous lymphoid cells are found. 
The hilar sheath which surrounds the larger arteries and veins is in the form of a some- 
what thick investment of fibro-muscular tissue. 

In the Rabbit, Eat, and Guinea-pig the tunica propria consists mainly of white 
fibrous tissue, containing some connective tissue corpuscles and a few lymphoid cells. 
There is a small amount of unstriped muscle, chiefly in the deeper portion of the capsule, 
which does not amount to a layer in the rabbit and the rat, but in the guinea-pig forms 
about the inner fifth of the capsule ; most of the fibres are transverse, some are longi- 
tudinal, and these are more numerous near the hilus than elsewhere. The tunica 
propria contains a considerable number of elastic fibres which are especially numerous 
in the rat. The trabeculas are somewhat thick but not dense. They are composed of a 
mixture of white fibrous tissue and of unstriped muscle, and are relatively more muscular 
than the capsule, which is accounted for by their being derived from its deeper part. In 
the rat the trabecular framework is more strongly developed, and the trabecules contain a 
greater proportion of muscle than in the rabbit and guinea-pig. The hilar sheath is, 
in each case, feebly developed, and contains little muscle. 

In the Hedgehog, as. in the Eodentia, the tunica propria consists chiefly of white 
fibrous tissue. There is a thin layer of muscle next the parenchyma, and there are a 
few muscle fibre cells scattered throughout the thickness of the capsule. Contrasting 
with the scarcity of muscle there is an abundance of elastic tissue. The trabecular 
system is somewhat more strongly developed, and contains more muscle, than in the 
Rodentia. The trabecules break up into small secondary ones that resemble the 
microscopic trabecules found in the spleen of the Ungulata. The hilar sheath is well 
developed. There is a well-developed muscular outer layer, between which and the 
outer surface of the artery lies a considerable quantity of areolar tissue containing 
lymphoid cells, and forming the early stage of an adenoid sheath. This does not appear 
immediately after the arteries have separated from the veins, but after their second 
bifurcation. (Plate I. fig. 2.) 

In the Human Spleen the tunica propria is composed almost entirely of white fibrous 
tissue. There is a small amount of yellow elastic tissue associated with a little muscle. 
The spindle-shaped muscle fibre cells are practically confined to the deeper portion of 
the capsule, and are slightly more numerous near the., origin of the trabecules. The 
trabecular framework is only slightly developed. The trabecules consist chiefly of 
white fibrous and elastic tissue. They have only a small amount of muscle, but follow 



260 DE A. J. WHITING ON THE 

the rule in being relatively more muscular than the capsule. The hilar sheath is 
well developed. Its outer portion is somewhat strongly muscular. The muscle fibre 
cells are arranged both longitudinally and transversely. 

Summary regarding the Supporting Framework of the Spleen. 

1. The variation in the supporting framework of the spleen appears to be mainly 
in two directions, one in the degree of its muscularity, and the other in the degree of 
the development of the trabecular system. 

2. I would here emphasise the fact that the hilar sheath around the vessels is 
muscular as well as the trabecular, and, as I have several times already implied, its 
muscularity varies with that of the capsule as a whole, and is therefore in the aggregate 
less than that of the trabecular, which resemble the deeper muscular portion of the 
tunica propria. Klein * and Bannwarth t have noticed the presence of muscle in the 
hilar sheath. 

3. As the supporting framework of the spleen becomes less strongly developed in 
the higher animals, and as its muscularity decreases, the elastic element increases. 

4. I think it is important to regard the hilar sheath as outside the essential splenic- 
substance, as, in fact, an inflection of the capsule. 

5. The trabecular system proper appears to be peculiar to the Mammalia ; where it is 
represented in the lower vertebrates it probably corresponds with the hilar sheath and, 
except in the Ophidia, is feebly developed. 

6. Among mammals the trabecular system reaches its highest development, as far as 
I have observed, in the Carnivora ; its lowest, in the Cetacea. 

7. Unstriped muscle occurs in the framework of all the spleens that I have examined. 
At its minimum in the fish, it gradually increases in amount as the scale is ascended 
through the amphibians, the reptiles, the birds, to the mammals, and reaches its maximum 
among the Mammalia in the Ungulata or Carnivora, then gradually decreases through the 
Cetacea and the Eodentia (rising slightly, however, in the hedgehog) to Man. 

Chapter II. 

The Adenoid Sheath of the Splenic Arteries and the Splenic Follicles.\ 

As the splenic artery and nerves pass through the hilus of the spleen they are 
ensheathcd by the inflected capsule. The sheath consists of three strata : next the artery 
is a thin layer of loose areolar tissue, derived, in part at least, from the subperitoneal 
connective tissue, and probably in part from the tunica adventitia of the artery, contain- 
ing a few lymphoid cells ; then comes a layer of denser white fibrous tissue, derived from 
the outer layer of the capsule, containing a considerable number of connective tissue 

* Klein (10), p. 3C7. t Bannwarth (26). 

X The following general description is based on the examination of the spleen of the Kitten. 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 261 



corpuscles, a few lymphoid cells, and some strands of yellow elastic tissue ; and exter- 
nally is a layer of unstriped muscle derived from the inner layer of the capsule. 

Near the hilus this sheath surrounds both the artery and the vein, the latter haAang 
pierced the sheath at some distance internal to the hilus. Shortly after the artery has 
separated from the vein, there occurs within the hilar sheath a proliferation of lymphoid 
cells, which seems to begin in the innermost stratum — the layer derived from the sub- 
serous connective tissue. As the artery becomes smaller, the lymphoid cells increase 
greatly in number, and the sheath is represented by a small amount of white fibrous 
tissue together with the external muscular layer, which is itself much thinner. The 
arterial branch, thus surrounded by loosely arranged lymphoid cells, and externally by 
the remnant of the hilar sheath, divides in a dichotomous manner. The branches that 
result are similarly ensheathed, except that the investment of adenoid tissue varies in 
thickness, so that it resembles in some degree a nodose root, and that the remnant of the 
hilar sheath is thinner, and consists almost entirely of unstriped muscle. 

The nodosities of the adenoid sheath constitute the splenic follicles or Malpighian 
bodies, and the extension of the hilar sheath forms for them a capsule-like covering which 
is contractile, and probably also highly elastic. In a section of a follicle, whether the 
artery be cut transversely, obliquely or longitudinally, the cells of which the peripheral 
layer is composed always appear spindle-shaped. The obvious explanation of this is, 
that as spindle-shaped muscle fibre cells run in all directions over the follicle, adapting 
themselves to its spherical contour, those fibres alone that are in the plane of the section 
are seen with characteristic fusiform shape, while those cut obliquely or transversely 
appear as inconspicuous dots. This peripheral zone consists usually of two, three, or 
four loose layers of fibres ; and that it is continuous with the outer muscular layer of the 
hilar sheath is clearly seen when a longitudinal section of the artery and follicle is 
examined. Springing from the artery thin-walled capillaries run among the lymphoid 
cells, and they are more numerous, and consequently more conspicuous, towards the 
periphery of the follicle. 

The substance of the follicle consists of lymphoid cells, most of which are large and 
uninucleated, contained in the mesjies of an adenoid reticulum. Near the centre of the 
follicle, a few larger uninucleated or multinucleated lymphoid cells may be seen, and 
towards the periphery there is a narrow belt of small uninucleated lymphoid cells. 
Occasionally very large protoplasmic cells, four or five times the size of the largest 
lymphoid cells, are found near the centre of the follicle. Their protoplasm is coarsely 
granular and stains very deeply with eosine. Some of these cells appear to be non- 
nucleated ; in others there is a single nucleus at the margin of the cell, and they often 
exhibit round vacuoles. 

The intrafollicular reticulum consists of delicate branching threads, that anastomose 
at irregular intervals. Upon the nodes of the network large, oval, connective tissue cells 
are placed. The meshes vary in size and the threads in fineness. The meshes are closer 
and the threads stronger towards the periphery. In addition to this reticulum there is 

VOL. XXXVIII. PART II. (NO. 8). 2 N 



'262 DR A. J. WHITING ON THE 

an intercellular substance of white or pearly appearance, which, after injection of the 
spleen through the artery with silver nitrate solution, appears as a brown network, in 
each mesh of which is a lymphoid cell. This network differs, therefore, from the adenoid 
reticulum in being regular in size of mesh, and in being equally distinct at all parts of 
the follicle. 

The adenoid sheath of the splenic arteries does not show any nodular swellings in 
the fish, amphibians, or reptiles, nor in some birds. In the Cod, after the splenic 
arteries have become somewhat diminished in size, while they are still accompanied by 
the branches of the splenic vein, their thick fibrous coat becomes infiltrated with lym- 
phoid cells. Except around the largest arterial branches, the matrix of this coat is not 
strongly fibrous, but resembles very fine areolar tissue or mucous tissue. The lymphoid 
cells are small, sparse, and stain deeply with hasmatoxylin. Among them red blood- 
corpuscles are occasionally seen, indicating the presence of capillaries. The artery 
with its adenoid sheath, together with the vein, and nerve trunks if present, are 
surrounded by the hilar sheath, at the periphery of which a few muscle fibre cells 
are seen. 

In the Skate there are groups of cells in relation with the walls of the splenic arteries. 
Each group is nodular and not unlike the splenic follicle of the higher vertebrate, with 
part at least of which it is probably homologous. They are conspicuous from their 
reddish-brown colour, and, while some are plainly connected with the arterial wall, 
others, which are cut at one side of the artery, appear isolated. The cells vary 
considerably in size — the smallest are about the size of an average lymphoid cell, and 
the largest are five or six times larger. The larger cells are each situated in a cell- 
space, and contain one or two nuclei imbedded in reddish-brown granular protoplasm, 
while the smaller consist of a single spherical nucleus surrounded by a mere rim of 
protoplasm. Many of the nuclei show evidence of division. The cells appear to be 
arranged in columns. Surrounding; each nodule is a belt of fibrous tissue derived 
from the hilar sheath, and outside that is a zone of lymphoid cells which fades away 
into the surrounding pulp. 

In the spleen of the Frog there is a grouping of lymphoid cells around the artery, 
without any localised accumulation. Loosely arranged clusters of cells are especially 
noticeable immediately under the capsule, most, if not all, of which are sections of the 
adenoid sheath. There is apparently no peripheral zone of fibrous tissue ; but among 
the cells were seen coloured blood-corpuscles contained within capillaries. 

In the spleen of the Tortoise the pulp and the adenoid tissue are nearly equal in 
amount : the latter is more abundant near the capsule, the former near the centre. The 
lymphoid tissue follows the course of the arteries in very broad bands, and nowhere 
shows localised accumulation. Not the arteries alone, but also the veins are surrounded 
by adenoid tissue as in the spleen of the skate. The artery while of considerable calibre 
is closely surrounded by a thin layer of very delicate fibrous tissue, outside which is a 
comparatively thick layer of adenoid tissue. As the artery becomes smaller the adenoid 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 263 

sheath becomes thinner, and the connective tissue sheath thicker, until the lymphoid 
sheath disappears when the latter persists as a thick, almost granular, investment of a 
thin-walled vessel. It contains several large, round or oval, clear cells, which stain faintly 
with hematoxylin. The capillaries are large, but not numerous, and therefore do not 
form a close network. The cells are contained in the meshes of a delicate fibrous 
reticulum, which seems to be continuous with that of the adjoining pulp. They are 
mainly of three kinds : — (1) Small, angular, deeply blue-stained lymphoid cells, which fill 
the greater part of the adenoid tissue ; (2) much less numerous cells, consisting of a large 
vesicular nucleus, surrounded by granular pink-stained protoplasm, that varies in amount 
in different cells. Such cells may, however, have a horse-shoe shaped nucleus, or two, 
three, or more somewhat large nuclei, or sometimes eight to twelve small, deeply blue- 
stained nuclei, in which case there is only a small amount of intermediate protoplasm ; 
(3) pink-stained granular cells occurring in clumps, which are situated in the delicate 
fibrous tissue that surrounds the artery. The characters of the cells, and their grouping, 
recall similar appearances found in the skate's spleen, but the cells in the skate are much 
larger. 

The spleen of the Grass Snake shows a cellular cortex and a fibrous medulla. The 
former is composed of four wedge-shaped masses of lymphoid tissue, the apex of each 
pointing to the centre. The latter consists of a four-rayed core of fibrous tissue, which 
contains large ramifying blood-sinuses, each pyramidal ray separating two wedges of 
adenoid tissue. Thus the base of the wedge is placed upon fibro-muscular tissue 
containing blood-sinuses, its sides are bounded by fibrous bands that contain blood- 
sinuses, and its blunt apex is imbedded in fibrous tissue that contains blood-sinuses. 
About the middle of each wedge there is a comparatively small artery, and running 
between the lymphoid cells are large, thin- walled, much branched capillaries that anasto- 
mose with each other to form a network, and open into the venous sinuses that are 
contained in the surrounding fibrous tissue. The cells of the adenoid tissue resemble those 
already described in the spleen of the tortoise. The protoplasmic cells are specially 
noticeable immediately outside the capillary wall. 

The Splenic Follicles make their first appearance in birds, but they do not occur in 
all ; for instance, they are absent from the spleen of the hawk. 

In the Rook the special artery of the follicle, as well as the capillaries, are of remark- 
ably large size. The follicles are almost invariably situated on one side of the artery, 
and not round it. Around the follicles there is a strong belt of muscle, which consists 
of two or three interlacing layers, and which may very clearly be seen to spring from the 
hilar sheath. (Plate I. fig. 3.) The cells are of two kinds : — (l) Large protoplasmic 
corpuscles having a single nucleus — similar cells occur plentifully in the pulp surrounding 
the follicles ; and (2) ordinary small lymphoid cells. These two kinds are indiscriminately 
mixed throughout the follicle. There is a delicate adenoid reticulum. 

In the spleen of the Ox the follicles are numerous and conspicuous. Two small 
arteries may occasionally be seen in one follicle, and fairly large capillaries run in its 



264 DK A. J. WHITING ON THE 

substance. The intrafollicular reticulum is fibrous but not very strongly developed. 
Many of the follicles possess a large-celled central area — the germinal centre of Flemming 
— which tends to fall away from the section. The cells of the follicle are of two kinds : — 
(l) Small, deeply stained lymphoid cells, which are often collected in clumps, and the 
clumps sometimes appear to be surrounded by a capsule; and (2) large, faintly stained 
cells, leucoblasts, grouped near the centre, but also occurring sparsely among the smaller 
ones, which consist of a large vesicular nucleus surrounded by a varying amount of finely 
granular protoplasm, that occasionally contains yellow pigment grains. There is a 
distinct zone of fine spindle-shaped muscle fibre cells, in two or three layers, bounding 
the follicle ; and outside that is a broad belt of tissue showing characters intermediate 
between those of the pulp on the one side and those of the follicle on the other, and is, 
in fact, the pulp containing the lymphoid cells, small and uninucleated, part of which 
have probably been pushed out by the cellular proliferation within the follicle, and part 
squeezed out by the contraction of the peripheral muscular layer. Although these cells 
are small, they are apparently somewhat larger than those in the outer part of the 
follicles. 

In the spleen of the Sheep the continuous adenoid sheath of the artery, along the 
course of the artery, between the follicles and the hilus, is very well developed. It is 
bounded externally by the thick muscular layer of the hilar sheath. The structure of the 
follicle resembles very closely that in the ox. But the artery is apparently of larger 
calibre, the capillaries are slightly larger, and the intrafollicular reticulum is somewhat 
more strongly developed. The lymphoid cells show the same division into zones, a 
large-celled germinal centre, a small-celled peripheral zone, and an extrafollicular 
aureola. 

In the spleen of the Pig the follicles are not quite so numerous as in the ox and sheep, 
and they are still less sharply defined from the surrounding pulp. Sometimes sections 
of three or four arteries may be seen in one follicle ; moreover, the artery may often 
be seen to branch within the continuous adenoid sheath without any division of the 
hilar sheath. In structure the follicles are almost identical with those in the ox and 
sheep ; the intrafollicular reticulum appears, however, to be more strongly developed. 
In the spleen of the young Pig the peripheral zone of muscle is more distinct than in 
the adult, as also is its origin from the hilar sheath. 

In the Cat the follicles are more numerous and larger, relative to the size of the 
spleen, than they are in the Ungulata. The intrafollicular capillaries form a very 
distinct network, and they may frequently be traced into the spaces of the pulp. 
The cells of the follicle in the adult cat are clearly divisible into two zones. In a 
central area, where the capillaries are most numerous, they are comparatively large, 
although they vary considerably in size ; some of them are uninucleated and others are 
multinucleated. The nuclei always possess a nucleolus, and the cells a definite outline. 
Some of the smaller central cells show evidence of division by transverse fission. The 
largest cells in the follicles are scattered and isolated, each contained in a cell space. 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 265 

Their protoplasm stains very deeply with eosine, and they usually possess a single, oval, 
somewhat small nucleus. In the outer zone the cells are smaller, more nearly uniform 
in size ; they stain more deeply with hsematoxylin and closely resemble free nuclei. 
They are arranged with considerable regularity in circular lines, the outermost circles 
being separated by long connective tissue strands derived apparently from the hilar 
sheath. At the periphery of the follicle is a zone of spindle-shaped muscle fibre cells, 
similar to the zone already described in the kitten, only not quite so distinct. 

In the spleen of the Dog the follicles are much like those in the cat's spleen. The 
special artery is immediately surrounded by a thick fibrous sheath, which seems to 
represent the original tunica adventitia of the artery. The intrafollicular reticulum is 
feebly developed. The follicular cells are divisible into three zones : the germinal 
central cells and those of the peripheral zone resemble the cells described in the cat's 
spleen ; the intermediate zone is composed of cells like those of the peripheral zone, 
but slightly smaller. There is a limiting belt of spindle-shaped muscle fibre cells, which 
is more prominent in the spleen, of the puppy than in the adult dog. In the spleen of 
the Puppy nearly all the cells of the follicle are like the central germinal cells ; smaller 
cells are found in a narrow ring at the periphery of the follicle, and plentifully in the 
pulp outside it. It seems to be the rule that the follicular cells are divisible into three 
zones in the adult alone. 

In the spleen of the Porpoise there are numerous accumulations of lymphoid cells, 
but they are not sharply defined. The intrafollicular capillaries are somewhat large 
and very conspicuous. They may occasionally be clearly seen to open into the spaces 
of the pulp. The lymphoid cells do not show any distinct division into zones. They 
resemble the cells in the germinal area of other adult, or those of the entire follicles 
of the young mammal. In many of the cells the nucleus is surrounded by a layer of 
protoplasm that stains deeply pink with eosine ; and very, large cells similar in character 
may sometimes be seen near the middle of the follicle. The follicles have apparently 
no fibrous limiting layer. Large venous trunks form a kind of boundary for them. 
In several points of structure this spleen resembles the reptilian spleen ; in the large 
venous spaces of the capsule, in the diffuse adenoid tissue partially surrounded by 
venous channels, and in the large size of the capillaries within the adenoid tissue. 
The macroscopic appearances of the spleens of the tortoise and porpoise are similar, and 
both are developed in the mesentery of the small intestine. 

In the spleen of the Narwhal the follicles are numerous but small, and the cells 
that form them, being of large size, are in comparatively small number. The artery 
divides simultaneously into a number of arterioles which run a nearly parallel course. 
There may be as many as eleven branches, and together they produce a characteristic 
brush-like appearance. A similar, although less pronounced, arrangement obtains in 
the pig's spleen. This bundle of vessels is contained in a matrix of fibrous tissue, that 
contains a few lymphoid cells, and forms a rudimentary adenoid sheath. When the 
arterioles separate from each other, lymphoid cells accumulate in the fibrous tissue 



266 DR A. J. WHITING ON THE 

matrix, and wide thin-walled capillaries run among them. This fibrous matrix is 
apparently derived both from the tunica adventitia of the artery and from the inner 
layer of the hilar sheath. The follicular cells appear to be of four kinds : (1) The majority 
are large round cells consisting of a round, deeply stained nucleus surrounded by a rim 
of protoplasm ; (2) smaller round cells, like free nuclei, staining even more deeply with 
hsematoxylin ; (3) cells the largest of all, pale and granular, containing a faintly stained 
vesicular nucleus ; (4) cells similar to the last, but found only in some follicles, 
containing numerous yellow pigment grains. At the periphery of the follicles is a 
remarkably distinct zone of muscle, composed of two or three layers of spindle cells. 

In the spleen of the Rabbit the follicles are numerous and well localised. The 
network of capillaries is unusually conspicuous. Some of the follicles in the adult spleen 
contain small but distinct germinal centres. The follicular cells are clearly divisible into 
three concentric areas. The largest cells are, as usual, in the central area, the smaller 
are in the peripheral zone, and the smallest are in the narrow intermediate zone. The 
germinal centre is marked off from the intermediate zone by a ring of fibrous tissue con- 
taining spindle-shaped nuclei. The cells in it are of four kinds : (1) Large cells, consisting 
of a big vesicular nucleus that stains blue with hsematoxylin, and a small amount of 
peripheral protoplasm that stains pink with eosine ; each of these is usually enclosed in 
a cell space : (2) somewhat smaller cells with a round, comparatively small and deeply 
stained nucleus surrounded by a relatively large amount of protoplasm ; occasionally 
seven or eight of such cells are found packed together in a cell space : (3) large pigment 
cells, occasionally seen : (4) small, deeply stained lymphoid cells, possessing a very 
small amount of protoplasm, if any, around a nucleus which contains a nucleolus. The 
last kind are specially numerous near the periphery of the germinal centre, and are 
evidently identical with the cells of the intermediate zone. The capillaries in the 
central area are larger than those in the other parts of the follicle. Surrounding the 
follicle is a zone of spindle-shaped cells, many of which are muscular, and external to 
it is a zone of pulp tissue especially rich in lymphoid cells. 

In the Rat the splenic follicles are remarkable in containing not only branching 
capillaries, but also, in many cases, branching arterioles. The intrafollicular capillary 
plexus is very distinct, both on account of the number of capillaries, and on account of 
the numerous endothelial nuclei in their walls that stain deeply with hsematoxylin. The 
cells resemble those in the follicles of the rabbit. Around the follicle is a layer of muscle 
fibre cells, together with a few strands of connective tissue. There is an extrafollicular 
belt of lymphoid cells, such as are found associated in other spleens with the germinal 
centre. The intrafollicular reticulum is unusually conspicuous. It is composed of 
delicate branching filaments, with clear, faintly blue-stained oval cells at the nodal points. 
It seems to be continuous on the one hand with the wall of the artery, and on the other 
with that part at least of the limiting fibrous layer that is composed of connective tissue 
strands. It is distinctly denser and stronger towards the periphery of the follicle. 

In the spleen of the Guinea-pig the greater part of the parenchyma is composed of 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 267 

lymph follicular tissue, which exists in the form of a continuous adenoid sheath around 
the artery. The intrafollicular capillaries are much less evident than in the follicles of 
other Eodents. The arrangement of the cellular elements is similar. The peripheral 
fibrous layer contains little muscle, resembling in this particular the hilar sheath and the 
tunica propria. 

In the spleen of the Hedgehog the follicles are few. The intrafollicular reticulum is 
very delicate, and the walls of the capillaries are very thin. The cells of many of the 
follicles show a germinal character near the middle of the follicle with the daughter cells 
outside. There is a well-marked limiting fibrous zone, composed principally of muscle, 
which is arranged in two or three layers. In this spleen the continuity of the peripheral 
muscular layer with the hilar sheath is very clearly seen. (Plate I, fig. 4.) 

In the spleen of the Child the follicles are neither numerous nor sharply defined from 
the surrounding pulp. The special arterial branch is large in relation to the size of the 
follicle. Between its muscular coat and the lymphoid cells there is a somewhat thick 
layer of loose fibrous tissue, which contains a few elliptical nuclei. The follicular capil- 
laries are neither conspicuous nor numerous ; their walls are very delicate, and contain 
few nuclei. They are most numerous near the middle of the follicle, and are often sur- 
rounded by a fibrous sheath derived from that of the artery. The intrafollicular 
reticulum is very strongly developed, and its outer portion seems to consist of the 
separated fibres of the inner layer of the hilar sheath. The cellular elements of the 
follicle are of two kinds, lymphoid cells and large protoplasmic corpuscles. In many 
follicles the latter are grouped around the artery so as to form a core that is surrounded 
by lymphoid cells. Such a core may occupy about a fourth of the entire follicle. The 
cells that form it are round, oval, or polygonal in shape, and consist of a round 
nucleus staining faintly blue with hematoxylin, surrounded by coarsely granular 
protoplasm, staining deeply pink with eosine. Although these cells are found princi- 
pally collected together in a central area, isolated examples also occur among the lym- 
phoid cells at all distances from the centre, and even at the periphery of the follicle. 

The cells vary much in size ; the smaller are usually near the middle of the core, and 
these are much less deeply stained than the larger ones, both as regards their protoplasm 
and nucleus. The nuclei are sometimes large, round, and vesicular, sometimes horse-shoe 
shaped, and occasionally two, situated at a considerable distance from each other, are 
connected by a slender filament of nuclear substance. There is evidence of division by 
karyokinesis as well as by simple transverse fission. Sometimes a large cell may be seen 
to be filled with deeply stained nuclei, a mere rim of pink-stained protoplasm remaining. 
Many of the cells, and especially the larger ones, are vacuolated. 

The origin of these cells can as yet only be conjectured. Frequently they appear to 
spring from the fibrous sheath of the artery and capillaries of the follicle. But such 
cells occur also in the arterial lumen, both intrafollicular, and while surrounded by the 
hilar sheath alone. Stilling* in 1886 described " bright centres" in the follicles of the 

* Stilling (21), p. 18. 



268 DR A. J. WHITING ON THE 

human spleen ; he considers that they are pathological, and that they are composed of 
" epithelial elements." He found them only in emaciated individuals, and once in a case 
where death was registered as due to anaemia following haemorrhage. They are, according 
to our own observation, constant in the child's spleen (the structure of which is always 
of necessity doubtfully normal), but we have found similar cells in the follicles of a 
strong adult dog (which was certainly ill nourished and probably also anaemic), in those 
of a healthy kitten, and in other healthy animals. It seems to us, therefore, that they 
are not necessarily pathological. Around the follicles there is a zone of fibrous tissue, 
consisting of tw r o or three layers of nucleated fibres, derived from the hilar sheath. 

In the Human Foetus the cells of the follicles are large, and resemble the cells in the 
germinal centre of the lower mammals. Very rarely a cell may be seen resembling the 
protoplasmic corpuscles in the follicles of the child's spleen. The peripheral fibrous zone 
is more distinct than in the spleen of the child. 

In the Human Adult the majority of the follicular cells consist of a small, round, 
deeply stained nucleus, surrounded by a rim of granular protoplasm staining pink with 
eosine. Some of the cells are like free nuclei, and a very small number are large and 
granular, like the protoplasmic cells in the follicles of the child's spleen. The intra- 
follicular reticulum is more strongly developed than in any other spleen. 

Summary regarding the Splenic Follicles. 

1. In the fish, amphibians, and reptiles the lymphoid cells form a continuous sheath, 
of even thickness, around the artery. 

2. In mammals and in some birds the lymphoid cells accumulate in the form of 
nodular swellings — the splenic follicles — which occur at irregular intervals along the 
course of the arteries. 

3. The accumulation of lymphoid cells occurs between the hilar sheath and the artery. 

4. Large lymphoid cells (leucoblasts) occupy the middle of many of the follicles in 
the adult spleen (forming the germinal centre as described by Flemming in lymphatic 
glands), and by their division give rise to small uninucleated lymphoid cells (as pointed 
out by Mobius *) which are extruded into the pulp. The small cells are produced both 
by direct division and by indirect karyokinesis. 

5. The intercellular substance of the follicles consists of two elements, a delicate 
adenoid reticulum (Muller t, W.) and a viscid albuminous substance (Huxley }). 

G. TJie follicles are surrounded, except where the artery enters and leaves, by a 
fibro-muscular covering, which is a remnant of the hilar sheath. 

This covering is not a separate membrane, as Sanders § thought, neither is it a 
condensation of the pulp reticulum as stated by most observers and recently by 
Bannwarth.|| 

* Mobius (19), p. 343. + W. Muller (12), p. 355. X Huxley (7), p. 81. 

§ Sanders (3), p. 82. || Bannwarth (26), pp. 379, 381. 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OP THE SPLEEN. 269 

Chapter III. 
The Ellipsoidal Sheath of the Splenic Arteries and the Splenic Ellipsoids. 

The smaller arteries in the Kitten's spleen, after leaving the follicles, divide 
dichotomously into several branches, each ending in a bulbous swelling, termed by 
W. Muller an ellipsoidal capillary sheath, or simply an ellipsoid. The thick-walled 
vessel passes for a short distance into the substance of the ellipsoid and is continued 
either as a single thin-walled vessel running in its long axis and leaving it undivided at 
the opposite pole, or more usually divided into several such vessels which leave at 
different points. Each emergent vessel opens into the blood-sinuses of the pulp. 
As the name implies, they are usually oval in shape ; they are sometimes nearly round, 
and sometimes pyriform. Each is composed of several rings of nucleated spindle cells, 
which are probably muscular, arranged concentrically around the axial vessel or vessels, 
and imbedded in a granular ground substance. In addition to the rings of spindle 
cells, which are more strongly developed near the periphery of the ellipsoid, there are 
scattered at irregular intervals throughout its substance a few lymphoid cells. At the 
margin of each there is a layer of spindle-shaped cells, and the whole is suspended in a 
blood-sinus by the vessels that enter and leave. 

In the spleen of the Skate the smallest arterial branches are enveloped in a some- 
what thick fibrous sheath, but this does not show any localised swelling. In the 
spleen of the cat-fish, Pouchet * has described cylindrical bodies, circularly striated 
and containing nuclei, which apparently resemble those described in the spleen of the 
kitten. 

In the spleen of the Cod, after the arteries have become much reduced in size and 
separated from the veins, they are surrounded by a continuous sheath of almost 
structureless tissue, which, varying in thickness, has an undulating surface and is oval 
in section. To distinguish it from the circumscribed ellipsoids it may be termed the 
ellipsoidal sheath. Imbedded in it are a few large clear cells arranged concentrically, 
and also here and there smaller lymphoid cells that stain more deeply withhaematoxylin. 
The ellipsoidal sheath has apparently no limiting membrane, but there is a peripheral 
blood-sinus in which, together with red blood-corpuscles, are numerous deeply stained 
lymphoid cells, which are mostly crowded at the edge of the ellipsoidal sheath, and 
resemble the smaller cells contained in it, and also those forming the adenoid 
sheath. Separating adjacent blood-sinuses are trabeculse-like strands of fibrous tissue 
containing two or three layers of spindle cells, which strands are apparently the remnant 
of the hilar sheath. A reticulum of fine fibres may sometimes be seen to stretch 
between these strands and the opposite surface of the ellipsoidal sheath. 

In the spleen of the Frog there does not appear to be any ellipsoidal sheath like 

* Pouchet (18), p. 501. 
VOL. XXXVIII. PART II. (NO. s). 2 



270 DR A. J. WHITING ON THE 

that in the cod, but only a somewhat thick fibrous sheath around the smaller arteries 
as in the skate. 

In the spleen of the Tortoise, after the lymphoid sheath of the artery ceases, its 
fibrous sheath (tunica adventitia) becomes thicker ; the axial vessel becomes smaller, 
and shortly divides into two or more branches which ultimately open as thin-walled 
vessels into the venous sinuses of the pulp. The tissue forming the substance of the 
sheath is so finely fibrillated as to be almost granular. It contains a few large, vesicular 
lymphoid cells like those of the tunica propria and hilar sheath, which appear to 
multiply, sometimes, if not always, by transverse fission. The outline of the sheath is 
irregular, and in some places there is the appearance of a delicate structureless limiting 
membrane. There is often the appearance of a venous sinus around the sheath, but 
sometimes its outer wall seems to be connected with a fine reticulum. 

In the spleen of the Grass Snake there does not seem to be any structure homo- 
logous with the ellipsoidal sheath. 

In the Hawk, as the muscular coat of the splenic artery grows thinner the fibrous 
coat becomes thicker, until it forms a sponge-like investment containing lymphoid cells. 
The muscle fibre cells derived from the hilar sheath seem to form a limiting layer /or 
the ellipsoidal sheath. It is composed of a strong fibrous network, that stretches 
between the peripheral muscular layer and the vessel wall, in the meshes of which are 
a few clear, faintly stained lymphoid cells. It is suspended in a capacious venous 
sinus, within which the cellular elements of the pulp are found, and across which the 
fine fibres of a delicate reticulum are sometimes seen to stretch. 

The spleen of the Rook contains numerous circumscribed ellipsoids, which resemble 
in general characters those found in the spleen of the kitten. Into each ellipsoid an 
arteriole enters, and from each, at one or more points, a thin-walled vessel leaves, while 
from the axial vessel capillaries destitute of endothelium radiate outwards to the 
surface. The afferent is distinguished from the emergent vessel by the character of 
its endothelial lining ; in the former this is composed of spindle-shaped cells occurring 
at considerable intervals, in the latter of rounded cells placed near together. The 
endothelium changes in character almost immediately after the entrance of the arteriole, 
and it again becomes flattened shortly after the vessel has left the ellipsoid. 

In shape the ellipsoids are usually oval, but sometimes trifoliate. Their substance 
consists of cells, spindle-shaped or round, imbedded in a structureless ground substance. 
The round cells are either small lymphoid cells like free nuclei, that stain deep blue 
with hasmatoxylin, or protoplasmic cells, twice, thrice, or four times the size of the 
former, consisting of a small, round nucleus surrounded by granular protoplasm, and 
resembling the cells in the follicles. The spindle cells are concentrically arranged 
around the axial vessel. Running between the round cells, in addition to the capillaries, 
are highly refractile lines which look like strands of elastic tissue. 

In almost every instance there are indications of an investing membrane of spindle- 
shaped cells, apparently muscular in nature. This enveloping layer is evidently a 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 271 

vestige of the hilar sheath ; longitudinal fibres are seen to be continuous between the 
two, and also between both and the peripheral layer of the follicles. The ellipsoids are 
usually seen to be surrounded by a clear space, probably a venous sinus, but this has 
not a distinct outer wall. 

In the spleen of the Pigeon, around the terminal portion of the arteries, there is a 
short length of ellipsoidal sheath, similar to the extended sheath in the spleen of the 
hawk. It consists of a granular undifferentiated matrix, in which are imbedded a few 
clear faintly stained nuclei, but no concentric spindle cells. There is a clear space 
surrounding it, across which the strands of a delicate reticulum stretch, as in the spleen 
of the hawk ; and there are considerable numbers of lymphoid cells grouped around the 
sheath, as in the spleen of the tortoise. But there does not appear to be any definite 
layer at the periphery of the sheath, nor any separating the venous sinus from the pulp. 
Thus the ellipsoidal sheath in the spleen of the pigeon seems to afford a connecting link 
between the extended ellipsoidal sheath in the spleens of the hawk, tortoise, and cod, and 
the circumscribed ellipsoid in the spleen of the rook, and in the spleen of many mammals. 

In the spleen of the Ox, as in the spleen of the pigeon, the arterial terminations are 
surrounded by short lengths of an ellipsoidal sheath. There is a comparatively clear 
area surrounding each stretch of ellipsoidal sheath, from which the microscopic trabeculse 
of the pulp are absent, and in which run numerous anastomosing venous sinuses. (Plate 
II. fig. 5.) As compared with the ellipsoids of some other ungulate animals, its most 
striking feature is its length : it is seven or eight times as long as it is broad. In outline 
it is irregularly undulating, and may be compared to a much gnarled club. An arteriole, 
having lost its muscular coat, runs in a wavy manner through the long axis of the 
expansion, but it does not apparently give off any capillaries, nor does it divide, but 
opens as a thin-walled vessel into the venous sinuses of the surrounding clear area. The 
substance of the sheath consists of a granular ground substance that stains deeply pink 
with eosine, in which are imbedded large, round or oval cells having a well marked 
intranuclear network. These vary in size and also in depth of staining with hsema- 
toxylin, and, while most are lymphoid cells resembling free nuclei, others have a rim of 
hyaline protoplasm that stains deeply pink with eosine. Similar cells are sometimes 
seen lying free near the sheath. There are occasionally large vacuoles in the granular 
matrix. At the periphery of the sheath is a membrane containing spindle-shaped 
nuclei, and surrounding that is a venous sinus which apparently communicates with the 
sinuses of the clear area. 

In the spleen of the Sheep there are numerous ellipsoids,' which are sometimes lobed, 
but are usually in the form of a long oval. The axial vessel retains its muscular coat 
for a short distance, and frequently divides into two or three thin- walled vessels before 
leaving the ellipsoid to open into the venous sinuses of the pulp. Breaks in the con- 
tinuity of the wall of the axial vessels are frequently seen, but no distinct capillaries 
were observed. The substance of the ellipsoid consists of a fibrous network, at the nodes 
of which are faintly stained cells like connective tissue corpuscles. The meshes some- 



272 DR A. J. WHITING ON THE 

times contain red blood-corpuscles, suggesting that the apertures in the wall of the 
axial vessel may lead directly into the spaces of the network. There are, in addition 
to the network, a few spindle cells arranged concentrically around the axial vessel. 
There is a well marked limiting membrane, which is sometimes seen to be composed of 
unstriped muscle. In most cases the ellipsoid is seen to be surrounded by a venous sinus. 

In the spleen of the Pig the ellipsoids resemble closely those in the sheep, but the 
fibrous reticulum and the limiting layer are not so strongly developed. In their substance 
are concentrically arranged spindle cells, lymphoid cells, and protoplasmic corpuscles. 
There is an appearance of circular muscular fibres in the wall of the axial vessel, more 
delicate and wider apart than those in the arterioles. A wide venous sinus surrounds 
the ellipsoid and communicates with the veins of the pulp. 

In the spleen of the Dog the ellipsoids are round or oval in transverse section ; but 
in longitudinal section their outline is irregular, being prolonged into angles at the places 
of emergence of the vessels, so that their shape is sometimes like that of a multipolar 
nerve cell. (Plate II. fig. 6.) A somewhat large arteriole enters the ellipsoid, and 
divides into two or three branches which leave it at different points. As in the ellipsoids 
of the pig, the axial vessel appears to possess a thin circular muscular coat. From the 
sides of the axial vessels spring numerous delicate, wavy, capillary vessels, destitute of 
endothelium, which anastomose to form a plexus and open into the peripheral blood- 
sinus. In transverse section the lumen of the capillaries sometimes seems to be of 
considerable size, quite large enough to transmit a red blood-corpuscle. 

The substance of the ellipsoid consists of a fibrous reticulum with connective tissue 
corpuscles at its nodes, and lymphoid cells in its meshes, together with a small amount 
of granular matrix. The reticulum is like that in the ellipsoid of the sheep, but is not 
so strong and has smaller meshes. Appearing to form a part of the reticulum are a few 
spindle cells arranged concentrically around the axial vessel. There is a limiting layer 
formed of a somewhat strong membrane and spindle-shaped cells, or nuclei. Surround- 
ing each ellipsoid is a capacious venous sinus, that contains cells similar to the cellular 
elements of the pulp and red blood-corpuscles. The peripheral sinuses communicate 
with each other by thin- walled channels, and similarly with the venous sinuses of the 
pulp, and with the small veins that are laterally attached to the trabecule. One cannot 
help being struck with the number of points of resemblance between the ellipsoids and 
the follicles — the axial vessel, the radiating capillaries that anastomose, the peripheral 
layer sometimes muscular, the fibrous reticulum, the lymphoid cells — but in each of these 
particulars there is difference as well as resemblance. 

In the ellipsoids of the spleen of the Cat the arrangement of vessels is similar to 
that in the dog, as also is their substance, except that it is a little denser. There is 
a distinct limiting layer of spindle-shaped cells, but the peripheral blood sinus is not 
always distinct in the adult cat (although it nearly always is in the kitten) ; it is 
indeed sometimes nearly obliterated in the adult, apparently from compression by the 
surrounding pulp. 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 273 

In the spleen of the Porpoise there does not seem to be anything corresponding 
to the ellipsoids, and in the Narwhal the terminal arteries are merely invested by a 
somewhat thick fibrous sheath that contains a few lymphoid cells. 

In the spleen of the Rabbit the arteries, after leaving the follicles, are invested by 
a continuous fibro-cellular " ellipsoidal sheath." The fibres are usually spindle-shaped, 
and are arranged both longitudinally and concentrically. Within long meshes formed 
by them, lymphoid cells are found. There is an indistinct blood-sinus at the periphery 
of the sheath, something like that in the tortoise and rook. In the Rat and Mouse 
there is a similar ellipsoidal sheath, which is, however, surrounded by a well-marked 
blood-sinus. In the Guinea-pig a similar sheath forms septa between some of the 
large sinuses of the pulp. 

In the Hedgehog the ellipsoids are numerous and conspicuous. In transverse 
section they are round ; in longitudinal section they are seen to be oval, or not 
unfrequently trilobed. The vessels are arranged as in the dog and cat. The axial 
vessel has a distinct circular coat consisting apparently of delicate muscle fibres 
placed at long but regular intervals from each other. The substance of the ellipsoids 
consists of a considerable amount of a granular ground substance, in which are 
imbedded numerous clear, uninucleated lymphoid cells, and of an ill-developed 
fibrous reticulum that contains many concentrically arranged spindle cells, which 
are in all probability muscular. There is a well-developed external layer composed 
of strong fibres having long nuclei, which are almost certainly muscular. Surrounding 
the ellipsoid is a somewhat narrow venous sinus. 

In the Human Spleen after the arteries leave the follicles they are continuously 
invested by a fibro-cellular ellipsoidal sheath as in the spleen of the Rodents. It is 
composed of a network of strong connective tissue strands which, near the periphery, 
is denser and composed of fibres arranged mainly longitudinally, and in the meshes 
of this network are some lymphoid cells. At first the sheath is about twice the 
thickness of the diameter of the vessel, but as the artery becomes smaller, the sheath 
becomes thinner ; the lymphoid cells decrease in number until they practically disappear, 
while the fibres persist so as to form a longitudinal sheath until the vessel opens into 
the spaces of the pulp. 

Commentary. 

The ellipsoids were first noticed by Billroth # in the spleen of the bird, and have 
since been described by Schweiggek-Seidel^ under the name of the capillary sheath, 
in the pig, dog, and cat, later in the same animals by W. Muller J and Kyber,§ and 
still later by Pouchet|j in the Selachian cartilaginous fish. Since the preceding 
observations were made they have been described by Dr Bannwarth 1F in the spleen 
of the cat, and, as we can testify, with fulness and accuracy. He has, however, failed 

* Billroth (8), p. 97. t Schweigger-Seidel (10), p. 465. t W. Muller (12), p. 360. 

§ Kyber (13), p. 561. j| Pouchet (18), p. 498. 1 Bannwarth (26), p. 398. 



274 DR A. J. WHITING ON THE 

to notice the peripheral blood-sinus, and consequently, as we think, falls into error 
of observation in some correlated points. He states,* for example, that the network 
of the ellipsoids is continuous with that of the pulp, while, as a matter of fact, the 
two are separated by a blood-sinus and a special envelope. He notices t the fine 
canals unlined by endothelium in the substance of the ellipsoid, but thinks that they 
all terminate in the meshes of the reticulum, while we believe that most of them, if 
not all, after anastomosing with each other, open into the peripheral blood-sinus. 
He is able to state positively! that the concentrically arranged nuclei are those of 
muscle fibres. To Kyber § belongs the credit of observing the presence of blood- 
channels at the periphery of the ellipsoids ; he, however, did not recognise that they 
were cavities or sinuses, but looked upon them as capillary veins. Klein, || differing 
from all authors, considers that the axial vessel of the ellipsoid is not a capillary but 
a minute artery, and as regards several animals we are able to confirm his observation. 
W. Muller H describes the termination of a nerve fibre in an ellipsoid, but this single 
observation has never been confirmed. 

Many different views as to the significance of the ellipsoids have been advanced; 
Billroth ** thinks they correspond with the adenoid sheath of the Amphibia; Schweigger- 
Seidel tt that they serve to filter the blood ; Kyber JJ that they are merely local swellings 
of the arterial sheath ; and Bannwarth §§ looks upon them as foci for the transformation 
of the tissue of the arterial sheath into pulp tissue, and that they serve to narrow the 
blood stream. We can agree in some measure with all of these views, except the 
former part of the last, for we think that they are the representative of the adenoid 
sheath, and they are swellings of the tissue of the arterial sheath, and also that they 
ma) 7 filter the blood by allowing the blood plasma to escape through the minute 
capillary channels into the peripheral sinus while the corpuscular elements of the 
blood are retained in the axial vessel. But we also think that they may be relics 
of the continuous ellipsoidal sheath of the lower vertebrates, and would suggest that 
they may subserve the function both of contractile bodies on the course of the main 
vessel, and of expansile bodies within capacious blood chambers ; that they may serve 
to minimise the effect of the pulse wave, transmitting the blood more gradually from 
the relatively very large arteries to the thin-walled blood spaces of the pulp, to empty 
at the same time by their expansion the peripheral blood-sinus, and by their contraction 
to help the flow of blood through the emergent veins. 

Summary regarding the Ellipsoidal Sheath and the Splenic Ellipsoids. 

1. The terminal portion of the splenic arteries in the Teleostean fish, in the tortoise, 
and in the hawk is invested by a continuous ellipsoidal sheath, which consists of a homo- 
geneous ground substance containing a few lymphoid cells. 

* Bannwarth (26), p. 403. t Bannwarth (26), p. 415. J Bannwarth (26), p. 404. § Kyber (13), p. 562. 
|| Klein (17), p. 426. 1 W. Muller (12), p. 360. ** Billroth (8), p. 97. 

tt Schweigger-Seidel (10), p. 971. %% Kyber (13), p. 562. §§ Bannwarth (26), p. 431. 



COMPAKATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 275 

2. In the Mammals it is invested either, as also in the rook, by a circumscribed sioell- 
ing of an ellipsoidal sheath — an ellipsoid, or by a continuous stretch of an ellipsoidal 
sheath, both containing a few lymphoid cells and some concentrically arranged spindle 
cells (that are probably, sometimes at least, muscular) imbedded in a homogeneous 
ground substance, while the former possesses a fibrous network, and the latter longitudi- 
nally arranged fibres in addition. 

3. The sheath is surrounded by a venous sinus which separates it from the pulp, 
and which has distinct ivalls in those Mammals alone that have circumscribed 
ellipsoids. 

4. The ellipsoids have a special nucleated covering, which in some instances is 
muscular. 

5. The axial vessel of the ellipsoid has, at least sometimes, a circular muscular coat. 

6. The axial vessels, in many animals, give off capillary channels which have no 
endothelial lining, and which anastomose before opening ultimately into the blood-sinus 
that surrounds the ellipsoid. 

7. The axial vessels end by leaving the ellipsoid as thin-walled veins which open 
into the spaces of the pulp. 

8. The peripheral blood-sinus of the ellipsoid communicates directly with adjacent 
ellipsoidal sinuses and splenic veins, but not with the emergent vessel of another 
ellipsoid. 

9. The ellipsoid is associated with greater muscularity of the supporting frame- 
work of the spleen than the ellipsoidal sheath. 



Chapter IV. 
The Splenic Pulp. 

In the spleen of the Dog the pulp consists of a reticulum formed by the anastomos- 
ing processes of branching cells, the meshes of which contain several kinds of free 
cellular elements. 

The supporting cells of the pulp consist of a cell plate, from which numerous radiat- 
ing plate-like processes pass, and in the middle of which is a round or oval nucleus. 
The cell plate and processes are transparent, homogeneous or -slightly granular, and stain 
faintly pink with eosine. When the plate-like processes are cut longitudinally they 
appear as long thin fibres. (Plate II. fig. 7.) The reticulum seems to be sometimes 
directly continuous with the terminations of the smallest trabeculse, also with the under 
surface of the capsule, with the sides of the larger trabeculse and of the hilar sheath, and 
with the walls of the venous sinuses. But it apparently is not connected with the 
reticulum of the follicles, and differs from it in nature, inasmuch as the latter seems to 



276 DR A. J. WHITING ON THE 

consist, like the reticulum of a lymph gland, of a network of fibres with cells super- 
imposed at the nodes. 

The corpuscular elements of the pulp are mainly of four kinds : — (l) Round or oval 
lymphoid cells, measuring 3-7 v-. in diameter, which stain deeply with hsematoxylin, 
and resemble the cells forming the outer zone of the follicles. They have only a very 
small amount of peripheral protoplasm, if any. (2) Protoplasmic corpuscles of oval shape, 
consisting of a round or oval nucleus surrounded by a considerable amount of pink- 
stained protoplasm,* and measuring 7-10 m. in diameter. (3) Cells containing pig- 
ment resembling in size and shape the protoplasmic corpuscles. (4) Giant cells, consisting 
of coarsely granular protoplasm which stains deeply pink with eosine, and in which are 
imbedded several nuclei. The usual shape of these cells is lobed oval, and their average 
measurement is about 30 m long by 15 m broad. 

In the Skate the reticulum of the splenic pulp is composed of a branching system of 
expanded fibres which stain faintly with eosine, and which are connected with narrower, 
stronger, more deeply stained fibres. The expanded fibres are sections of the plate-like 
processes of branching nucleated cells. The narrower stronger fibres seem to be the 
walls of the venous radicles ; they are frequently crescentic in shape, and have on their 
inner concave surface a layer of endothelial cells. 

The cells of the pulp are of four principal kinds : — (1) The most numerous are clear, 
round cells like free nuclei. They stain faintly with hsematoxylin, the chromatin 
particles being arranged in a ring near the periphery of the cell. Their average size 
is about 8 /x,. (2) Less numerous cells consisting of granular protoplasm that stains 
pink with eosine, surrounding a round, oval or horse-shoe shaped nucleus. These cells 
resemble some of the cells contained in the representatives of the follicles. (3) Cells like 
the protoplasmic corpuscles, but containing pigment granules of different sizes. These 
resemble the majority of the cells of the follicles. (4) Cells similar in size and shape to 
the third variety, but vacuolated, the vacuoles containing rounded particles of pigmented 
protoplasm which have no nuclei and are about a fourth of the size of the coloured blood- 
corpuscles. 

In the Cod and Ling the reticulum of the splenic pulp consists of anastomosing plate- 
like processes of nucleated cells as in the skate, but the meshes are apparently wider. 
The cells of the cod's spleen are mainly of three kinds: — (l) Round lymphoid cells of 
different sizes, sometimes possessing a narrow rim of protoplasm, but usually like free- 
nuclei. (2) Protoplasmic corpuscles varying in size from about a half to a little more 
than the size of their average red blood-corpuscle. Both protoplasm and nucleus stain 
with hsematoxylin, the former faintly, the latter somewhat deeply. The larger have the 
size and shape of the coloured blood-corpuscles. (3) Cells containing pigment occur 
here and there in clumps. 

* Whenever the phrases "pink-stained protoplasm" and "blue-stained nuclei" occur in the text they mean 
respectively "protoplasm that has been stained pink with eosine" and "nuclei that have been stained blue with 
hematoxylin." 



COMPAEATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 277 

In the spleen of the Frog the reticulum of the pulp consists of large branching cells, 
the plate-like processes of which do not taper so much before joining with others as in 
the spleen of the fish. The processes are so much expanded that sometimes the sec- 
tional area seems to be chiefly occupied by them, the meshes appearing as comparatively 
small fenestra? in a nucleated membrane. When the processes are seen in oblique 
section or in profile, they appear like narrow bands in the one case or somewhat fine 
threads in the other. (Plate II. fig. 8.) Each cell contains usually one large, oval, 
slightly granular, faintly blue-stained nucleus, but there are sometimes two, three or 
four. The meshes of the reticulum vary much in size and shape. The processes of the 
cells of the reticulum appear to be continuous with the walls of the venous sinuses, and 
to join the outer wall of the artery. 

The cells of the pulp are mainly of five kinds in addition to the red blood-corpuscles : 
— (1) Round lymphoid cells resembling free nuclei are far the most abundant. They vary 
in size from a half to four or five times the size of the nucleus of a red blood-corpuscle. 
(2) Round protoplasmic corpuscles apparently identical with the small leucocytes. Their 
size is a little more than half that of the red blood-corpuscles, and they are composed 
of finely granular protoplasm, staining faintly pink with eosine, in which is imbedded 
sometimes a single small round nucleus that stains somewhat deeply blue with hsema- 
toxylin ; but more usually there are two or three such in a single cell. (3) Large proto- 
plasmic corpuscles about twice the size of a red blood-corpuscle, which seem to be iden- 
tical with the large leucocytes. They are best seen in the intracapsular venous sinuses, 
but are far more numerous in the parenchyma immediately underneath the capsule. 
They consist of somewhat finely granular protoplasm, that stains faintly blue with hsema- 
toxylin, and from three to eight faintly stained nuclei. They sometimes show very 
large karyokinetic figures. (4) Round or oval cells, found especially near the middle 
of the pulp, about the size of the small leucocyte, whose protoplasm is in the form of 
round coarse granules, which stain very deeply pink with eosine, each having a single, 
oval, blue-stained nucleus. These probably correspond with the eosinophilous cells of 
Waldeyer. (5) Cells containing pigment are especially numerous in the outer zone of 
the parenchyma and particularly in the winter frog. In shape they are round or oval, 
and are similar in size to the large leucocytes. They have a single nucleus usually, but 
sometimes they are multinucleated. The smaller consist of granular, faintly blue-stained 
protoplasm, in which are scattered numerous dark brown granules. The larger appear 
to consist almost entirely of pigment particles, the nucleus being pushed to the peri- 
phery of the cell. The cells appear sometimes to be vacuolated. In very thin sections, 
some of the larger pigment masses are seen to be composed of oval parcels of pigment 
granules, each parcel being about the size of a red blood-corpuscle, and containing a 
faintly blue-stained nucleus near its margin. This appearance suggests that each oval 
parcel may be a degenerated red blood-corpuscle. The pigment does not blacken with 
ammonium sulphide. 

Within the intracapsular venous sinuses of the winter frog, and in the summer frog, 

VOL. XXXVIII. PART II. (NO. 8). 2 T 



278 DR A. J. WHITING ON THE 

more especially in the pulp immediately under the capsule, the red blood-corpuscles may 
be seen in various stages of transformation. In some the perinuclear protoplasm shows 
here and there faintly blue-stained areas ; in others the whole of the protoplasm is 
slightly blue-stained ; in other cells the blue staining of the protoplasm is almost as 
deep as that of the nucleus, and in others the nucleus cannot be distinguished. The 
protoplasm breaks up into round, blue-stained, coarse granules, which at first appear to 
be imbedded in a blue-stained homogeneous matrix, but are subsequently apparently free 
within a cell capsule, when the position of the nucleus is indicated by an oval shaded 
area near one pole of the cell. Ultimately the granules escape from the cell capsules, 
and collect into large irregular masses that adhere to the walls of the venous sinuses, or 
pass down by the venous channels into the parenchyma towards the larger veins near 
the middle of the spleen. 

In the spleen of the Tortoise the reticulum of the pulp closely resembles that of the 
frog's spleen. The cells that form it are, however, smaller and more delicate, and they 
have more processes. The meshes are usually oval or round, but near the walls of the 
veins, where the cell processes are thread-like, they are angular. The supporting cells are 
continuous with the trabecular sheath of the veins, and with the inner muscular layer of 
the capsule. The reticulum of the periarterial adenoid tissue seems to be continuous 
with that of the pulp, but the former is altogether finer, the cell processes are thread-like, 
and they stain more faintly with eosine. 

There are at least six different kinds of cells in the pulp ; these are : — (l) Lymphoid 
cells, similar to those of the adenoid sheath but slightly larger, without peripheral proto- 
plasm, and like free nuclei. (2) Protoplasmic corpuscles of round or oval shape, which 
vary considerably in size but are usually four or five times larger than a lymphoid cell. 
Each has usually a single nucleus, which is round, and at least half the size of the whole 
cell. The protoplasm is finely granular, and stains deeply pink with eosine. Similar 
cells, but smaller and staining more deeply with eosine, occur in clumps here and there 
throughout the pulp. (3) There arc a few eosinophilous cells, which are more numerous 
just under the capsule than elsewhere. (4) Scattered in large numbers throughout the 
pulp are very small cells, oval, or nearly round, each having a single, round, deeply 
stained nucleus. The whole cell is about a half and the nucleus about a fourth of the 
size of a lymphoid cell. The rim of perinuclear protoplasm is hyaline and stains but 
slightly with eosine. The nucleus is almost vitreous in appearance, and has no nucleolus. 
(5) There is a small proportion of cells that contain pigment, which are about ten times 
larger than the lymphoid cells. Each has a single nucleus, little if any protoplasm, and 
is filled with golden yellow granules. Sometimes a cell may be seen having not only 
pigment granules but also granules that stain very deeply with eosine like those of the 
eosinophilous cells. (G) Giant cells occur in considerable numbers. They vary much in 
size, from about 16 to 22 ft in diameter. They consist of granular protoplasm that 
stains not very deeply with eosine, in which is imbedded one large round nucleus, and 
often in addition several small nuclei that resemble lymphoid cells in size and shape, and 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 279 

generally stain more deeply with hsernatoxylin than the large nucleus. The protoplasm 
is frequently vacuolated, the vacuoles being usually about a fourth of the size of a red 
blood-corpuscle. Occasionally there is an appearance of a particle of protoplasm lying 
free in a vacuole. In shape the cells are usually oval but frequently irregular and 
sometimes almost spinous. Their general appearances are much like those of the giant 
cells found in the dog's spleen. (Plate II. fig. 9.) Within the intracapsular venous 
sinuses, as in the frog's spleen, are granular bodies that are evidently breaking down 
coloured blood-corpuscles. 

In the spleen of the Grass Snake there is no true pulp. It is probably represented 
by the opened out fibrous tissue of the supporting framework, that contains numerous 
protoplasmic corpuscles, some lymphoid cells, and a few pigment-holding cells. The 
only reticulum present is that of the adenoid tissue. 

The spleen of the Hawk resembles in many particulars the spleen of the bony fish ; 
in both, the pulp is rudimentary, and the greater part of the parenchyma consists of the 
ellipsoidal sheath. There are, however, areas of parenchyma around the veins that 
appear to represent the pulp. There is in them a feebly developed reticulum consisting 
of nucleated cells with thread-like processes, in the meshes of which are a large number 
of protoplasmic corpuscles, a few characteristic lymphoid cells, and very numerous red 
blood-corpuscles. 

In the spleen of the Pigeon the reticulum of the pulp is much more delicate than that 
of either the frog or tortoise ; the cells forming it are smaller, the cell plate extends only 
a little way beyond the nucleus, and the cell processes are longer, more slender, and more 
numerous. Its meshes are usually oval and comparatively large, but sometimes they are 
smaller and nearly round. 

The cells of the pulp are in the young pigeon apparently all small lymphoid cells, 
but in the adult there are in addition a few protoplasmic corpuscles, like the larger cells 
of the follicles, and a small number of pigment-holding cells. As in the spleen of the 
tortoise, some of the protoplasmic corpuscles occur in clumps ; they stain more deeply 
with eosine, and are contained in the meshes of a somewhat stronger reticulum. 

In the spleen of the Rook nearly all the cells of the pulp are large protoplasmic 
corpuscles like those in the follicles. 

In the spleen of the Pig the reticulum of the pulp consists of nucleated cells that give 
off processes, which are usually broad and plate-like, but sometimes narrow and fibre-like. 
In a cell with broad processes they are few in number and comparatively short, and in 
cells with slender processes the converse as a rule holds true ; the processes in the former 
case by their anastomosis form nearly round meshes, in the latter case elongated elliptical 
meshes. 

The reticulum appears to be directly continuous with the numerous microscopic 
trabecule of the pulp, the two blending without any appreciable line of junction. 
Often nearly parallel longitudinal ridges pass from a trabecula into an expanded portion 
of the reticulum, and these seem to be continuous with its muscular fibres. 



280 DE A. J. WHITING ON THE 

In the pulp of the adult spleen there are four kinds of cells : — (1) Lymphoid cells, 
which measure from 4-5 fi, stain deeply with hematoxylin, and resemble the cells of 
the outer zone of the follicles. (2) Protoplasmic corpuscles, measuring 6-8 jjl with 
usually a single, round, deeply stained nucleus, which is surrounded by a narrow or broad 
rim of hyaline protoplasm. (3) Coarsely granular or eosinophilous cells occur in small 
numbers, and vary in size correspondingly with the protoplasmic corpuscles. The largest 
are oval, and their very coarse granules obscure the nucleus if such is present. (4) 
Pigment-holding cells are in some spleens exceedingly numerous, in others quite sparse. 
They are usually oval in shape and measure from about 15 /a to 20 /x longitudinally by 
about 12 (jl in breadth. The pigment grains are of a yellow colour, and are of irregular 
size and shape ; they are surrounded by a cell wall, but there is apparently no protoplasm 
between them. An oval, blue-stained nucleus is sometimes to be seen about the middle 
of the cell. The cells tend to adhere firmly to the reticulum. 

In the splenic pulp of the Young Pig, aged three months, similar cellular elements 
are to be found, except pigment-holding cells, and there are in addition giant cells. 
(Plate II. figs. 10 and 11.) 

The giant cells vary considerably in size, but their average measurement is about 
30 /x in length and 18 /x in breadth. They are not by any means numerous : on an 
average about sixty are present in each section.* Their characteristic shape is oval. 
Their substance is a coarsely granular protoplasm, which stains of a deep pink colour 
with eosine, and which in the unstained condition is of a yellow colour. They have 
usually several nuclei, oval or round in shape, which are frequently connected together 
by threads of nuclear substance, but more often they appear to be isolated. Some of 
the smaller giant cells have only one large nucleus. The isolated nuclei of the 
multinucleated forms are sometimes near the middle of the cell, but usually near 
its periphery ; their average size is 5-8 ft. Near the margin of many of the giant 
cells are rounded vacuoles, in size a little larger than the nuclei ; in some that are 
situated quite close to the periphery of the cell there may be seen a deeply stained 
nucleus. Sometimes there is a mouth-like opening at the margin of the cell, which 
is probably the result of the rupture of a vacuole, and occasionally a vacuole is seen 
to be connected with the surface by a somewhat narrow channel, thus forming a 
pyriform space. 

Clustered near the margin of the giant cells, usually at points corresponding with 
the mouth-like openings, are cells that have the character of erythroblasts. Their 
usual measurement is 9-10 /x in diameter. They are round or oval in shape, and 
consist of a deeply blue-stained, round nucleus, that has a well-marked intranuclear 
network, but no nucleolus, which is surrounded by a rim of hyaline protoplasm, which 
stains deeply with eosine, and is of a yellow colour when unstained. The nuclei arc 

* By the term " section " in this relation is meant a section through the entire spleen at its thickest part in its 
transverse axis. In giving the number of giant cells in a section in the different spleens, my aim is to afford a basis for 
a rough comparison between the spleens. Each section contains only a portion of each of the giant cells enumerated. 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 281 

a little larger than the isolated nuclei of the giant cells ; they measure 7-8 m in diameter, 
and they stain somewhat less deeply with haematoxylin. They have sometimes a 
rather wide rim of protoplasm and sometimes two nuclei, while some of the cells 
lying near the open mouths of vacuoles appear not to have any perinuclear protoplasm. 
Cells similar to these occur in clumps at frequent intervals throughout the pulp. 

In two spleens of foetal pigs similar giant cells were found, but in them the 
vacuolation is not so pronounced, and there is less isolation of their nuclei. The 
latter are sometimes in the form of a convoluted chain, and occasionally numerous 
pyriform nuclei radiate outwards from the middle of the cell, their apices pointing 
inwards. The giant cells in the foetal spleen are slightly less numerous than in the 
spleen of the young pig, and they are also a little larger, their average measurement 
being 30 fi by 22 //,, as compared with 30 fi by 18 ju,. 

In the adult Ox and Sheep the splenic pulp very closely resembles that in the 
adult pig, so that one description may serve for the three ungulate animals. 

In the spleen of the Dog the cell processes that form the reticulum are much less 
expanded than those in the pig, and the whole reticulum is more delicate. 

Giant cells were present in the spleens of five dogs that were examined. In the 
spleens of three adult dogs they were comparatively few in number, about fifteen in 
each section ; in the spleen of a half-grown dog they were more numerous, about fifty 
in a section ; and in the spleen of a puppy they occurred in large numbers, on a rough 
estimate, about a thousand in each section. 

In the spleen of the adult Dog they were mainly situated in the neighbourhood 
of the follicles. In one spleen a comparatively small giant cell with four or five nuclei 
was separated from the artery of the follicle merely by two rows of lymphoid cells, 
and a similar giant cell, with eight or nine nuclei, was placed just outside the same 
follicle. In another adult spleen giant cells occur in groups about the middle of the 
follicles, and others are in the pulp immediately surrounding them. At the periphery 
of one follicle there was found a giant cell only partly in the pulp : it measured 28 /a 
by 16 ju,. In another follicle there were seen six or seven somewhat large giant cells, 
the largest of which (measuring 30 ft by 14 /x) had a single, large, round nucleus (about 
13 ii in diameter), while in the adjoining pulp there was a multinucleated giant cell, 
and in a neighbouring venous sinus a mass of protoplasm similar to that of the giant 
cell, but apparently non-nucleated. This spleen was obtained from an ill-nourished 
and probably slightly anaemic dog. 

In the spleen of the half-grown Dog some of the giant cells had vacuoles in their 
substance and also mouth-like openings on their surface. The nuclei of the giant 
cells showed great diversity of arrangement. Frequently seven or eight faintly stained 
nuclei were packed together near the middle of the cell in the form of a sphere. 
Sometimes a cell had three or four large, round nuclei, the cell protoplasm showing 
indication of division corresponding with each nucleus. The most common appearance 
was a number of oval nuclei arranged near the middle of the cell close to, but not 



282 DR A. J. WHITING ON THE 

touching, each other. Occasionally the nuclei have the shape of grains of corn. 
Near a giant cell that was apparently breaking up, a nucleus, unsurrounded by 
hyaline protoplasm, was seen to be connected by a thread of chromatin with the 
nuclei of the giant cell, which was still surrounded by granular protoplasm. A 
noticeable feature of this spleen was the large amount of pink-stained granular material 
present in the larger veins. 

In the spleen of the Puppy the cells of the pulp were mainly of three kinds : — (l) 
Round, small, deeply stained cells, measuring 4 n in diameter, which in the pulp 
have a very faint rim of perinuclear protoplasm, and in the veins have a distinct 
rim. (2) Round or oval protoplasmic corpuscles, the erythroblasts, occur in numbers 
throughout the pulp and in the veins. Their hyaline protoplasm stains deeply pink 
with eosine, and their nucleus has no nucleolus, but an open intranuclear network. 
The diameter of the cell varies from 7-10 m, that of the nucleus from 6-8 m. (Plate 
II. fig. 12.) (3) The giant cells resemble closely those described in the spleen of 
the young pig ; they show similar vacuoles and mouth-like openings. A vacuole 
usually contains either a small deeply stained cell like the homogeneous connected 
nuclei of the giant cells, or a protoplasmic corpuscle consisting of a large, clear, faintly 
stained nucleus, with characteristic intranuclear network, surrounded by a rim of 
hyaline or very finely granular protoplasm. The average measurement of the giant 
cells was about 36 by 28 /*. Their main substance consists of coarsely granular 
protoplasm which stained deeply pink with eosine, but at the periphery of the cell 
there was a zone of hyaline protoplasm which varies in breadth from a sixth to a 
third of its radius. Sometimes these two kinds of protoplasm are apparently separated 
by a narrow circular cleft, and often the hyaline rim seems to have separated like a 
rind from the granular core. The protoplasm of the giant cells, and also of the 
protoplasmic corpuscles, has a distinctly yellow colour in the unstained condition, 
similar to, but fainter than, that of the red blood-corpuscles, and both stain deeply 
with eosine. 

Most of the small, deeply stained, apparently homogeneous nuclei, when near the 
centre of the cell, are connected by chromatin threads, but other nuclei, always isolated 
and usually near the periphery of the cell, are faintly stained, vesicular, and have a 
conspicuous intranuclear network. Similar nuclei are sometimes seen in buds or large 
bulgings of the giant cell, and occasionally such a nucleus, surrounded by a rim of 
protoplasm, is contained, apparently within a vacuole, in the substance of the cell, and 
seems to be of the same kind as erythroblasts surrounding the giant cell. (Plate II. 
fig. 12.) Sometimes all the nuclei are faintly stained and vesicular, then they appear 
to be unconnected with each other and nearly fill the cell. The giant cells sometimes 
show indications of division by multiple karyokinesis. They are sometimes to be found 
within the larger veins in the substance of the spleen. 

In the spleen of the Cat the reticulum of the pulp closely resembles that in the 
dog's spleen, but the meshes seem to be slightly smaller and the cell processes somewhat 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 283 

plate-like. The cellular elements of the pulp in the adult spleen are mainly lymphoid 
cells, small and uninucleated, like those of the outer zone of the follicles ; but a few are 
larger and resemble the cells of the germinal centre. Protoplasmic corpuscles are 
comparatively few in number. Several spleens of adult cats were examined, and in only 
one of them giant cells were found, and in it there were not more than four in a section. 
Their nuclei were nearly always clustered in a ball near the middle of the cell, round 
which was found a comparatively narrow band of granular protoplasm that had a 
distinctly yellow hue when the section was stained with hasmatoxylin only. 

The cellular elements in the young and functionally active spleen show marked 
differences. The spleens of five kittens, of different ages, were examined — one six 
weeks old, one ten days, one about a week, one three days old, and one at birth, and 
in all of them the conspicuous feature is the presence of giant cells. These are most 
numerous in the seven days' spleen, numbering on a rough estimate about ten thousand 
in a section, and, as one would expect, the whole spleen was much enlarged. In the ten 
days old spleen they number about five hundred in a section, in the six weeks' spleen 
about fifty, in the three days' spleen about forty, and in the spleen at birth about 
twenty in a section. 

In the Kitten at birth the giant cells appear to be especially situated in the pulp 
that surrounds the smaller veins. Their average size is 20 /x in length by 30 /a in 
breadth. The cell protoplasm has a conspicuous hyaline rim, which has a more pro- 
nounced yellow colour than the rest. In most of the cells the nuclei are grouped 
centrally, but in some as many as eight nuclei are scattered throughout the substance 
of the cell, and occasionally a knob-like portion of a nucleus that is attached or apposed 
to the central heap projects beyond the general outline of the cell. A few of the 
giant cells show vacuoles. Around the giant cell are frequently grouped cells having 
the characters of erythroblasts. There are with them similar but smaller cells with 
more deeply stained nuclei. 

In the three days old Kitten the cellular elements are practically the same in 
character as those of the newly-born kitten. The nuclei of the giant cells are nearly 
always collected in a spherical heap near the centre of the cell. A remarkable feature, 
as in the spleen last described, is the presence of large oblong free masses of pig- 
ment both in the pulp and in the veins. Although the colour of the red blood- 
corpuscles is slightly the darker, there is a strong presumption that the invariable 
yellow colour of the giant cells and of the erythroblasts is due to the presence of 
haemoglobin. 

In the spleen of the Kitten about a tveek old the nuclei of the giant cells are 
usually grouped together near the middle of the cell, and the groups are frequently 
separated from the protoplasm by a perinuclear space. When the individual nuclei are not 
close together, they are often seen to be connected by threads of chromatin. Some of the 
groups of nuclei are practically unstained with hematoxylin, while those of neighbouring 
cells may be deeply stained. The giant cells are much more irregular in outline than 



284 DR A. J. WHITING ON THE 

those in the spleens of the younger kittens ; the knobs or lobes seem to be formed and 
bounded by the mouth-like openings on the surface of the cell. Karyokinetic figures 
are to be made out in the edant cells. When the cells are treated with nuclear stains 
alone their protoplasm is seen to have a markedly yellow colour, which, since the tissue 
was fixed with alcohol only, could not be referred to the use of Muller's fluid or other 
coloured reagent. 

Young giant cells, a fourth or a fifth the size of the larger ones or less, with 
coarsely granular protoplasm and undivided nucleus, are somewhat numerous. Most of 
the giant cells are contained within cell spaces that are apparently formed from the 
connective tissue strands of the pulp stroma. Grouped in clusters among the giant 
cells are many erythroblasts, which have an unusually large amount of perinuclear 
protoplasm, which, like that of the giant cells, stains of a characteristic reddish-violet 
colour; when no staining agent has been used, it has a yellow tinge. Portions of 
broken down giant cells occur at frequent intervals throughout the pulp and in numbers 
within the veins, and in the smaller veins especially are quantities of coarse discrete 
granules that are apparently derived from the giant cells. 

In the spleen of the ten days old Kitten the giant cells show rather more numerous 
isolated nuclei than those in the spleens of the other kittens, and many contain erythro- 
blasts within their substance. Similar cells are more frequently seen within foveolse at 
the surface of the giant cells than in other spleens, and there is more vacuolation of the 
giant cells and more erythroblasts grouped round the giant cells than in the two 
younger spleens ; but while more vacuolation of the giant cells is present than in the 
seven days old spleen the erythroblasts are not more numerous. Within the veins 
in the interior of the spleen are numerous giant cells, erythroblasts, smaller nucleated 
red cells, and, in addition to the ordinary red blood-corpuscles and leucocytes, there 
are masses of granular protoplasm that are apparently derived from disintegrated 
giant cells. 

In the spleen of the Kitten six weeks old the giant cells do not show indications 
of active change as in the two immediately preceding spleens. Their nuclei are usually 
in a spherical group near the middle of the cell, which is surrounded by a comparatively 
narrow zone of yellowish granular protoplasm. The nuclear heap occasionally shows 
slight but large budding, corresponding with which is a large lobing of the cell 
protoplasm. Protoplasmic corpuscles with the characters of erythroblasts are compara- 
tively scarce. 

In the spleen of the Porpoise the reticulum is well developed and is more regular 
than any yet described. The cells composing it are characteristically stellate, and their 
delicate thread-like processes spring from a comparatively small cell plate. In addition 
to the rounded meshes there are many long narrow meshes bounded by connective 
tissue like strands. The whole stroma resembles more connective tissue than endo- 
thelium. 

The cellular elements of the pulp are mainly of three kinds: — (l) Lymphoid cells; 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 285 

(2) small hyaline protoplasmic corpuscles, many if not all of which are erythroblasts ; and 

(3) giant cells. 

The protoplasmic corpuscles are numerous, occurring both around the giant cells 
and generally throughout the pulp ; they have the usual characters of erythroblasts, 
a round nucleus with a pronounced intranuclear network and diffuse chromatin, but 
with no nucleolus, and a more or less narrow rim of perinuclear protoplasm, which is 
hyaline, of a yellow tint, and which stains very deeply with eosine. Around the giant 
cells and within the veins are similar but smaller cells, in which the nucleus of the 
erythroblasts seems to have become condensed, so that it is relatively and absolutely 
smaller and much more deeply stained : these cells are the ordinary nucleated red blood- 
corpuscles. There are appearances of karyokinesis in the nuclei of the erythroblasts. 

The giant cells resemble those found in other spleens, but they vary more in size 
and are on the whole smaller ; while the larger measure about 30 ju, by 18 fi, the smaller 
measure about 18 /a by 10 ju,. Most of the smaller have a single, somewhat large, oval 
nucleus, and some contain a relatively large number of vacuoles. They are all much 
lobed and their nuclei show active budding. Frequently they appear to be broken up, 
so that each isolated nucleus has a covering of protoplasm and forms a separate cell, 
while a considerable part of the protoplasm is apparently left without any nucleus. 
Giant cells are not unfrequently seen within the lumen of the veins. 

In the spleen of the Namvhal the majority of the cells are round protoplasmic 
corpuscles, consisting of a large round nucleus, that has a well-developed intra- 
nuclear network but no nucleolus, which is surrounded by a rim of hyaline yellowish 
protoplasm that stains of a reddish-brown colour with eosine. These cells are 
almost certainly erythroblasts; they measure about 10 /a in diameter and their 
nucleus about 8 ju,. The perinuclear rim of some cells is filled with coarse round 
granules that stain deeply with eosine. There are similar smaller cells, whose 
nuclei stain very deeply, and which possess a slightly broader rim of perinuclear proto- 
plasm ; these are almost undoubtedly nucleated red blood-corpuscles. Both kinds of 
cells are found in the veins. Giant cells are present in considerable numbers ; the 
smaller consist of a much lobed nucleus or central heap of nuclei surrounded by a rim 
of hyaline yellow protoplasm ; the larger show more pronounced budding of the 
nucleus. Sometimes a cell resembling the erythroblasts is contained within the 
substance of the cell near its periphery (as was described in the spleen of the puppy), 
and similar cells are clustered in numbers around the giant cell, many of them being 
in apposition with it and contained in cavities on its surface. The nuclei of the giant 
cells are sometimes completely separated from each other, and there is an appearance, 
similar to that described in the spleen of the porpoise, as if the giant cell were breaking 
up to set them free. 

In the spleen of the Rabbit the reticulum of the pulp varies little from that of the 
dog ; the cells forming it are more numerous in a similar sectional area, and are more 
delicate. They are typically stellate, their nuclei are often large, oval, and stain faintly 

VOL. XXXVIII. PART II. (NO. 8). 2 Q 



286 DR A. J. WHITING ON THE 

with hematoxylin ; but sometimes they are small, nearly round and stain deeply. The 
cell plate and processes are clear and glassy. There are many long connective tissue 
strands in the stroma, some of which form the walls of the venous sinuses, and with them 
the stellate cells are directly continuous. 

The corpuscular elements in the pulp of the spleen of a young Rabbit (probably 
about half grown) are of four kinds : — (1) Lymphoid cells ; (2) giant cells ; (3) hyaline 
protoplasmic corpuscles or erythroblasts ; and (4) eosinophilous cells. 

The giant cells, which are in considerable numbers, about two hundred in a section, 
resemble those described in other animals. They show well marked karyokinetic figures. 
The cell protoplasm shows numerous vacuoles, some of which are apposed to the central 
nuclear heap. The erythroblasts are not very numerous, while they occupy a position 
around the giant cells as in other spleens. Eosinophilous cells are comparatively 
numerous : they often occur in groups that are composed sometimes of as many as twenty 
cells. 

In the splenic pulp of an adult Rabbit there occur all the kinds of cells met with 
in the preceding spleen, and also some cells of another sort. Within the venous sinuses 
especially, but also in the pulp, are a few cells about a third of the size of the giant cells, 
consisting of red-stained granular protoplasm that surrounds two or three nuclei, and 
a variable number of clear round areas which, although something like red blood- 
corpuscles, seem to be vacuoles. Only about four or five characteristic giant cells occur 
in a section. 

In the spleen of a second adult Rabbit the venous sinuses contain many such special 
vacuolated cells, and the cell substance between the vacuoles contains a large number 
of yellow pigment graiDS. The average diameter of these cells is about 16 /a, while the 
vacuoles measure about 6 /a. There are apparently no giant cells either in the follicles 
or in the pulp. 

In the pulp reticulum of the spleen of the Rat there are fewer long connective tissue 
strands than in that of the rabbit, their place being taken by muscular bundles derived 
from the trabecule, with which the supporting cells are continuous. These cells are not 
so characteristically stellate, and their processes, which are slightly more thread-like, branch 
and anastomose more, hence the meshes of the network are relatively more numerous 
and closer together, while the nuclei are relatively fewer. 

The corpuscular elements of the pulp in the adult Rat are of four kinds : — (l) 
Lymphoid cells of different sizes ; (2) erythroblasts ; (3) giant cells, larger and smaller ; 
and (4) pigment-holding cells. 

The giant cells are like those described in other spleens, they number about twenty 
or thirty in a section. Their nuclei sometimes contain so little chromatin as to be seen 
only with difficulty after staining with hematoxylin, while the diffuse chromatin of the 
nuclei of the ery throblast sometimes stains so deeply as to hide the network. The central 
nuclear heap often shows active budding. Those cells that seem to be small giant cells 
are only about a half or a fourth the size of the larger, but they are much more numerous, 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 287 

numbering several hundreds in each section. They may have one rather large nucleus, 
or two or three smaller, and their protoplasm is usually coarsely granular and vacuolated, 
sometimes showing differentiation into a hyaline rim and a coarsely granular core, and 
always staining deeply with eosine. 

Yellow granules are imbedded in some cells at intervals in the granular pink-stained 
protoplasm, often accompanied by a single nucleus and several vacuoles. Occasionally a 
faintly blue-stained nucleus may be seen within a vacuole, and sometimes a round piece 
of granular protoplasm. The pigment increases in amount until in some cells the 
granules stud the small remnant of protoplasm surrounding the nucleus and separating 
the vacuoles. 

In the spleen of a half-groivn Rat there are no giant cells, but numerous smaller 
vacuolated cells containing pigment, which are like those of the adult rat, but are usually 
slightly larger and more pigmented. They vary in size from about 12 ju, to 20 ju, in 
diameter, and the larger are not of greater size than similar non- vacuolated cells. Some 
of the vacuoles are twice or thrice the size of a red blood-corpuscle. The remnant of the 
original protoplasm varies in amount, and the pigment granules appear to be in the proto- 
plasm and not in the vacuoles. (Plate III., fig. 13.) There is usually one nucleus, but some- 
times two or three, generally situated near the periphery of the cell. Similar pigmented 
cells, some of which are vacuolated, are found in the follicles. 

In the spleen of a young Rat there are a few characteristic giant cells, about ten in a 
section, but there are apparently no smaller vacuolated cells. 

In the spleen of the Mouse the reticulum of the pulp resembles very closely that in 
the rat's spleen ; the cell processes are on the whole more plate-like. 

A characteristic feature of the spleen of the adult brown Mouse is the presence in its 
pulp of giant cells ; this holds good too for the white mouse, as pointed out by J. Arnold. 
In addition to the giant cells there are protoplasmic corpuscles, lymphoid cells, and 
pigment-holding cells. Lymphoid cells of the follicles show numerous karyokinetic 
figures ; and a similar association of giant cells in the pulp with active karyokinesis in 
the follicles w r as noticed in the spleens of the young rat and water-vole. 

The giant cells number about fifty in a section, and while some are small, most are 
large, measuring about 20 /a by 30 /*. Their protoplasm has a markedly yellow tint, 
and is for the most part coarsely granular, although in some cells there is a very thin 
hyaline rim. The outline of the cells is sometimes prolonged into spinous projections. 
In the isolated unhardened giant cell, as seen on examining the fresh pulp teased in 
methyl salt solution, numerous buds may be seen to project from the cell, perhaps four 
or five in number ; they look like basins turned downwards upon the surface of the cell. 
The periphery of the giant cell is seen in the fresh condition to have a distinct yellow 
colour, apparently from the presence of haemoglobin. 

The nuclei of the giant cells after fixation show many different forms, many of which 
are figured by Arnold ; the simplest form seems to be that of a horse-shoe shape — some- 
times the nucleus has the shape of an hour-glass — but the most frequent arrangement is 



288 DR A. J. WHITING ON THE 

that of a ring or hollow sphere. Some cells show many small, deeply stained nuclei, 
together with a few larger, faintly stained vesicular nuclei. Occasionally in a giant cell 
there are to be seen the figures of multiple karyokinesis ; sixteen or twenty V-shaped 
loops arranged in a ring around the equatorial plate ; or at each end of a nuclear spindle 
there may be a ring of loops. Sometimes a small, deeply stained nucleus may be seen 
at a considerable distance from the nuclear heap, and connected with it by a long thin 
strand of chromatin. 

Occasionally an erythroblast seems to be attached by a pedicle of yellow hyaline 
protoplasm, continuous with its perinuclear protoplasm to the surface of the giant cell, 
and more frequently erythroblasts are seen to be lodged in depressions of the surface of 
the giant cell. The erythroblasts show evidence of active division by karyokinesis ; 
often five or six cells lying close together all contain figures, and every field of the 
microscope shows numerous examples. Nucleated red corpuscles, as well as erythroblasts, 
are readily recognised in films of the fresh pulp fixed by corrosive sublimate. 

In the spleen of the Guinea-pig the pulp tissue is in small amount, being in the form 
of thin partitions that separate wide venous sinuses. Many of these partitions show a 
thin-walled axial vessel and correspond probably with the ellipsoidal sheath. The pulp 
tissue proper seems to be mainly collected around the trabeculse. 

The reticulum is almost identical in appearance with that of the rat. 

The cellular elements are of three chief kinds : — ( 1 ) Lymphoid cells, both uninucleated 
and multinucleated leucocytes ; (2) coarsely granular protoplasmic corpuscles; and (3) 
the special vacuolated cells. These si3ecial cells — the so-called blood-corpuscle holding 
cells — are very numerous, and occur principally in the venous sinuses. They measure 
from 8 to 16 m in diameter. The smaller consist of coarsely granular protoplasm that stains 
deeply pink with eosine, surrounding a single deeply blue-stained nucleus, and sometimes 
a round or oval vacuole. The larger cells have similar protoplasm, occasionally three or 
four large nuclei without any vacuole, but usually a single nucleus laterally placed, 
several vacuoles and yellow pigment grains. (Plate III. fig. 14.) The vacuoles sometimes 
take up nearly the whole of the cell, the remnant of the protoplasm and the nucleus 
together being in the form of a signet ring around them, the outlines of the vacuoles 
forming a reticulum that occupies the central cavity. The pigment granules are rarely 
in a vacuole, — they sometimes seem to be adhering to its inner aspect, — but are 
usually in the protoplasm that surrounds them. They sometimes accumulate so as to 
fill the whole cell. 

In the spleen of the Hedgehog the pulp reticulum has a close resemblance to that of 
the dog and cat ; its cells have many broad plate-like processes, and its meshes are much 
larger than in the spleen of rodents. It is seen to be continuous with the trabecule and 
with the walls of the venous sinuses. As in the spleen of the mouse, the presence of 
giant cells in the pulp is constant, and so is the presence of large coarsely granular pro- 
toplasmic corpuscles (many of which are vacuolated) in the germinal centres of the 
follicles. In each of seven spleens, obtained at different seasons of the year, considerable 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 289 

numbers of giant cells occur ; they are most numerous in a spleen obtained during 
hibernation (numbering about 1000 in a section) ; but they are nearly as numerous 
(about 800 in a section) in a summer spleen, obtained in July ; while in a March 
spleen they are less numerous (about 600 in a section) ; and at the beginning of 
hibernation in one (October) spleen they number about 250, but in another (November) 
spleen they number about 800 in a section. In each case the size of the spleen varies 
directly with the number of giant cells. 

The other kinds of cells present in the pulp are lymphoid cells, erythroblasts, and a 
few pigment-holding cells that are found principally within the hilar sheath around the 
larger arteries. 

There are well-marked karyokinetic figures in the giant cells, in the erythroblasts, 
and in the protoplasmic corpuscles of the follicles. The figures are most numerous, as 
regards the giant cells, towards the end of hibernation ; in a March spleen there are about 
twenty in a section, occasionally two are seen in one field of the microscope ; they were 
also fairly numerous in the spleens of two hibernating animals during the autumn 
(October and November) months. The converse obtained as regards karyokinesis in the 
protoplasmic corpuscles of the follicles ; figures were plentiful in the summer and autumn 
spleens, but scarce or absent in the hibernating spleens. 

The nuclei of the giant cells show much variety in arrangement ; the most frequent 
is that of a central heap of closely apposed nuclei, sometimes as many as fifty or sixty 
in one cell. Often there may be seen a large number of pear-shaped nuclei, not apposed 
but isolated, yet near together, arranged in a radiating manner, the ends of the stalks of 
the pear-shaped bodies being near the centre, and their rounded ends near the periphery 
of the cell. Occasionally all the nuclei are isolated round bodies scattered nearly 
regularly throughout the substance of the cell. Sometimes an oval nucleus is seen to be 
connected with the central heap by a long thread of chromatin, being apparently on the 
point of separation. In some of the giant cells there is a distinct perinuclear space, 
especially in those cells with large karyokinetic nuclei ; and frequently a vacuole or 
basin-shaped space may be seen on the central nuclear heap, the cavity of the vacuole or 
basin being continuous with, and apparently a bulging of, the perinuclear space. 

Giant cells, together with erythroblasts, are frequently found in the lumen of the 
larger splenic veins. 

In the Human Spleen the reticulum of the pulp is intermediate in character between 
that of the Carnivora and that of the Rodentia, and is more like the former than the 
latter. The cell processes branch more than in any other spleen, and the nuclei are less 
numerous, because the cell plates that contain them form a comparatively small propor- 
tion of the whole. The cell plates seem to resemble, more closely than in any other 
pleen, those of connective tissue corpuscles. 

A striking feature in the stroma is the presence of large numbers of spindle-shaped 
muscle fibre cells arranged side by side in the form of sheets, not unlike those in the 
Amphibians' mesentery. The smallest trabeculse, that consist almost entirely of muscle, 



290 DR A. J. WHITING ON THE 

seem to become frayed out and are applied to the walls of the venous sinuses as layers of 
long, characteristically spindle-shaped fibres running in the long axis of the sinuses and 
nearly parallel to each other in the one layer that belongs to each sinus. In transverse 
section these fibres appear as irregularly pyramidal blocks, of a deep red colour after 
staining with eosine, some of which contain a nucleus ; they are planted by their 
bases upon what appears to be a connective tissue basement membrane, and thus form 
a more or less nearly complete ring next the blood stream and are uncovered by endo- 
thelium. It follows that the venous channels, along their whole course, have a close 
relation with the muscular fibres of the trabecule. Some, at least, of these fibres appear 
to terminate in the supporting cells of the stroma. Their appearance in longitudinal 
view resembles that described by Frey as due to endothelial cells, and in transverse view 
seems to be like that described as barrel-hoop shaped rings of elastic tissue. (Plate III. 
fig. 16.) 

Four examples of the human fcetal spleen were examined, three of the child and one 
spleen of a healthy adult. 

In the spleen of the Foetus between the eighth and ninth month the cellular elements 
of the pulp are primarily of three kinds : — Lymphoid cells, protoplasmic corpuscles, and 
giant or special cells. The lymphoid cells are chiefly uninucleated leucocytes, and are 
comparatively sparse. The protoplasmic corpuscles are of four kinds : — (1) Smaller 
hyaline protoplasmic cells, consisting of a deeply stained round nucleus, that possesses a 
well-developed intranuclear network and measures about 5 \i in diameter, which is 
surrounded by a comparatively narrow rim of yellow hyaline protoplasm that stains 
deeply pink with eosine. These are the nucleated red blood-corpuscles. (2) Larger 
hyaline protoplasmic corpuscles resembling the nucleated red corpuscles, but having a 
relatively wider rim of perinuclear protoplasm. Their nucleus usually stains a little less 
deeply, and like that of the smaller cells has no nucleolus. The diameter of the cells 
measures about 8-10 ju,, that of the nuclei about 6-7 m- These are the erytkro- 
blasts of Lowitt. (3) Eosinophilous cells are comparatively numerous. (4) Coarsely 
granular protoplasmic corpuscles occur plentifully both in the pulp and in the follicles. 
Their protoplasm stains very deeply with eosine ; they have usually only one nucleus, 
but occasionally two or three ; they may or may not possess vacuoles. Some at least of 
them seem to be young giant cells. 

Among the special cells there appear to be intermediate forms between the ordinary 
giant cells, as found in the spleens of the lower animals, and the smaller special vacuo- 
lated cells, as found in the spleens of the rodent animals ; these special cells are of 
four main varieties : — (l) There are a few characteristic giant cells, perhaps three or 
four in a section, which measure on an average about 30 n by 20 m. (Plate III. fig. 
15.) Occasionally some of the nuclei are about twice as large as the others and are 
less deeply stained ; these are usually near the middle of the cell, while the smaller 
more deeply stained nuclei are near the periphery ; the latter measure from 4-6 v-. 
Sometimes a deeply stained nucleus, surrounded by a narrow rim of hyaline protoplasm, 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 291 

is attached to a giant cell by a conical pedicle of protoplasm continuous with and 
similar to the perinuclear protoplasm, which hyaline pedicle is contained within a 
crevice of the granular protoplasm of the giant cell. Such a cell has all the characters 
of an erythroblast. (2) Other cells more numerous than the ordinary giant cells 
(perhaps a hundred in a section), have many isolated nuclei of different sizes, most, but not 
all of which are contained within spaces that appear to be vacuoles ; a few seem to be 
imbedded in the original granular protoplasm. Some of the nuclei in the vacuoles are 
immediately surrounded by a rim of deeply pink-stained protoplasm. (Plate III. fig. 16.) 
Frequently the vacuoles near the surface of the cells, perhaps three or four in each, 
have no nuclei, and from other superficial vacuoles hyaline protoplasmic corpuscles 
appear to be escaping. (3) Probably the most numerous of the special cells are those 
consisting of a large number of nuclei, each of which is contained in a capsule-like 
space or vacuole, and all of which are surrounded by a comparatively thin membrane 
that consists of little if anything more than the outer portion of the wall of the outer- 
most vacuoles. (Plate III. fig. 16.) In some cells there are as many as thirty nuclei, 
each contained within a vacuole, and perhaps three or four of these have a rim of peri- 
nuclear protoplasm. These special cells vary much in size ; their average measurement 
is about 32 /u, by 38 jjl. The envacuoled nuclei likewise vary in size ; in some cells 
they are nearly all of comparatively large size, measuring about 8 /x, in other cells they 
are nearly all about half this size, but in most cells there are both large and small 
nuclei. The larger nuclei that stain less deeply have sometimes the appearance of 
karyokinetic change. (4) The fourth variety of the special cells consists of those in 
which the empty vacuoles are far more numerous than those that contain nuclei ; 
in some cells there are about twenty of the former and only two or three of the 
latter. Many of these cells closely resemble the special vacuolated cells — the so- 
called blood-corpuscle holding cells — in the spleen of the rodent animals. (Plate III. 
%. 17.) 

In the spleen of a Human Foetus probably between the seventh and eighth month 
there are a few similar multinucleated special cells which are not quite so large as 
those in the later foetus ; their average size is about 16 by 20 /x, and three or four may 
be found in a section. In the follicles are somewhat numerous coarsely granular 
protoplasmic corpuscles. Scattered throughout the pulp are many nucleated red blood- 
corpuscles, most of which appear to belong to the blood, but there are only a few 
erythroblasts. 

In another foetal spleen at about the seventh month similar special multinucleated 
cells occur in very small numbers ; and in slightly larger numbers the smaller vacuolated 
special cells like those that are found in the spleens of the rodent animals, but there 
are no characteristic giant cells. Eosinophilous cells are somewhat numerous ; nucleated 
red blood-corpuscles are still more numerous, but erythroblasts are scarce. 

In the spleen of a fourth Human Foetus between the fourth and fifth month 
there are a few somewhat small but otherwise characteristic giant cells, about four or 



292 DR A. J. WHITING ON THE 

five in a section. Coarsely granular protoplasmic corpuscles occur in the follicles 
and in the pulp ; in the latter are also numerous nucleated red cells and- a few erythro- 
blasts. 

In the spleen of the Child the' cellular elements of the pulp are mainly of four 
kinds : — Lymphoid cells, eosinophilous cells, numerous nucleated red blood-corpuscles 
and erythroblasts, and special cells of the type of giant cells. 

The special cells are of three kinds : — ( 1 ) There is a very small number of coarsely 
granular cells like small giant cells, their average measurement being about 20 by 
15 fx. They have usually two or three nuclei that vary considerably in size, and may 
or may not have vacuoles. (2) A few cells resemble those characteristic of the spleen 
of the eight months' foetus ; most of the vacuoles contain nuclei, the empty ones are in 
the proportion of one to three. (3) By far the most numerous are cells consisting of 
one or two oval nuclei and many vacuoles which are surrounded by a variable amount 
of granular protoplasm that stains somewhat deeply pink with eosine. Their usual size 
is about 20 jjl in diameter, but they may be 30 \l in diameter, and sometimes they are 
as large as 42 by 18 p. (Plate III. figs. 18, 19, and 20.) There may be four or five 
small vacuoles close to a central nucleus, all being surrounded by a broad band of 
coarsely granular protoplasm. Occasionally there are a few small vacuoles, together with 
a long oval nucleus, in a peripheral band of protoplasm, while the middle of the cell is 
occupied by a large vacuole that sometimes contains a round protoplasmic corpuscle 
whose diameter is about 10 /u, and that of its nucleus about 7 /x. More frequently, 
however, the cell contains so many vacuoles that its substance seems to consist almost 
entirely of their apposed capsule-like walls ; there is usually in addition a single 
almost elliptical nucleus surrounded by a little granular protoplasm at the periphery of 
the cell. These cells occur in large numbers within the venous sinuses, and the red 
blood-corpuscles by which they are surrounded adhere to their surface. The larger 
cells, found especially in the pulp, have usually two oval nuclei imbedded in a small 
amount of granular protoplasm and situated near the middle of the cell ; around them 
are frequently seen numerous erythroblasts. (Plate III. fig. 21.) Characteristic giant 
cells occur in some of the follicles ; they vary from about 50 by 20 fi to about a third 
of that size. In the pulp around the follicles are similar but smaller giant cells ; they 
have usually less protoplasm, more vacuoles, and a smaller nucleus. 

In the spleen of a Human Adult — a healthy man — the cellular elements of the pulp 
are lymphoid cells, eosinophilous cells, and coarsely granular protoplasmic corpuscles. 
The latter are most numerous near the follicles, while they occur in large numbers 
within the follicles. Their average size is about 8 /a in diameter ; they have usually 
a single round nucleus that measures about G /x, which has no nucleolus, but a well- 
marked intranuclear network. Occasionally one of the larger cells is seen to contain a 
large-budded nucleus. The smaller cells sometimes show ill-formed karyokinetic figures. 
These cells thus resemble very small giant cells rather than erythroblasts. 

There were no characteristic giant cells found in this healthy spleen. 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OP THE SPLEEN. 293 



Commentary. 

Our more accurate knowledge of the structure of the reticulum of the splenic pulp 
dates from 1875, when Dr Klein * published his observations on the structure of the 
spleen. My observations are almost entirely confirmatory of his ; I am in doubt, 
however, as to the exact nature of the cells that form it, for their character seems to me 
to be intermediate between those of endothelial cells and flattened branched connective 
tissue corpuscles, and rather to resemble the latter, as seen for example in tendon or in 
the cornea, than the former. I have never seen any indication of the production of 
lymphoid cells by budding from the cells of the matrix that he describes/I" nor the 
presence of pigment and coloured blood-corpuscles in the cell plates ; and I cannot 
accept his opinion that the giant cells form a part of the membranous stroma. J 

The chief interest in the study of the cellular elements of the splenic pulp seems to 
centre around those appearances that by some observers are believed to indicate a 
destruction, and by others a production of coloured blood-corpuscles. 

Tlie following evidence appears to me to he adverse to the theory of phagocy- 
tosis as regards the Giant Cells : — 

(1) They occur in the spleen at the time when blood formation has been proved to 
be taking place in it, — during late embryonic and early extra-uterine life, — just at those 
periods when one would expect loss of blood to be most disadvantageous. Although 
Van der Stricht § considers that they devour the extra vasated nuclei alone of erythro- 
blasts, Denys || believes that they take up the entire erythroblasts. (2) They occur in 
the follicles, where there are few if any coloured blood-corpuscles, and yet they do not 
take up the lymphoid cells. Erythroblasts are, however, found in the follicles around 
the giant cells, and in the mouth-like openings at their periphery. (3) Although the 
giant cells contain many empty vacuoles, we have never seen any partially digested 
nuclei in them. (4) If, as is more generally believed, the nuclei of nucleated red cells 
are absorbed and not extruded, there can be no free nuclei for the giant cells to devour. 
(5) Although the isolated nuclei that the giant cells contain, which are apparently 
identical in character with those of nucleated red cells or of erythroblasts, have no 
obvious perinuclear protoplasm of their own, as a rule, yet when near the periphery of the 
giant cell they have often a distinct rim of hyaline protoplasm, and are, in fact, entire 
erythroblasts. (6) The nuclei of contained erythroblasts may sometimes be seen to be 
connected with the central nuclear heap of the giant cell by a long and slender strand 
of chromatin. 

Summary regarding the Splenic Pulp. 

(1) The reticulum of the splenic pulp is formed by the anastomosis of the expanded 

* Klein (16), p. 368. t Klein (16), p. 369. 

% Klein (17), p. 426. § Van der Stricht (48), p. 88. 

|| Denys (24), p. 159. 

VOL. XXXVIII. PART II. (NO. 8). 2 R 



204 DR A. J. WHITING ON THE 

processes of nucleated plate-like cells, and is continuous with the supporting framework 
of the spleen. 

(2) The cellular elements of the pulp may be classified as follows : — 

1. Lymphoid Cells. 

(1) Uninucleated. 

(2) Multinucleated. 

2. Protoplasmic Corpuscles. 

(1) Coarsely granular. 

(2) Hyaline. 

(a) Erythroblasts. 

(b) Nucleated red cells 

(3) Eosinophilous cells. 

3. Pigment-holding Cells. 

4. Special Cells. 

(1) Giant cells. 

(2) Multinucleated vacuolated cells. 

(3) Uninucleated vacuolated cells. 

(3) The lymphoid cells are nearly all uninucleated, with little, if any, peripheral 
protoplasm, and resemble the small lymphoid cells of the outer zone of the follicles. 

(4) The multinucleated lymphoid cells have a considerable amount of finely granular 
protoplasm that stains faintly, if at all, with eosine ; and they are probably derived 
from the blood. 

(5) The protoplasm of the protoplasmic corpuscles stains deeply with eosine. 

(6) Erythroblasts and nucleated red cells are more numerous in those spleens that 
contain giant cells, and as a rule they appear to be most numerous in those that 
contain most giant cells. 

(7) Erythroblasts are sometimes seen in the substance of the giant cells, sometimes 
in bulgings of their surface, and often in mouth-like openings on their surface. 

(8) The erythroblasts multiply by karyokinesis. 

(9) The hyaline perinuclear protoplasm of the erythroblasts seems to be slightly 
tinted with haemoglobin as Bizzozero # maintained. 

(10) The pigment of the pigment-holding cells either occurs in the form of granules 
imbedded in a basis of coarsely granular protoplasm, or it, along with a nucleus, entirely 
fills the cell. It is probable that the pigment granules have been taken up by the 
pigment-cells, that the pigment-cells are phagocytes, and of the nature of leucocytes. 

(11) Giant cells occur, probably invariably, in the spleen of Mammals during early 
extra-uterine life, and usually also in late intra-uterine life. They occur in considerable 
numbers in the spleen of some small Mammals, for example the mouse, the rat, and the 
hedgehog, during adult life. And they may occur in small numbers in the spleen of 
individual instances of other adult Mammals, for example the dog and the cat. 

* Bizzozero, cited by Muir (47), p. 502. 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 295 

(12) Cells apparently homologous with the giant cells of the mammalian spleen were 
found in the spleen of the tortoise. 

(13) They seem to be a concomitant of the blood-forming activity of the spleen ; 
they are associated with numerous erythroblasts and nucleated red cells in the pulp, 
and frequently with active karyokinesis in the follicles. 

(14) They multiply usually by karyokinesis, but they probably divide sometimes 
by simple fission. 

(15) They have usually a large central nuclear heap that gives ofTpyriform buds. 

(16) The nuclear buds, when isolated in the cell, resemble the nuclei of nucleated red 
blood-corpuscles or of erythroblasts ; while near the middle of the giant cell they are 
somewhat small, stain deeply, and resemble the nuclei of the nucleated red blood- 
corpuscles : when near the periphery of the cell they are larger, they stain faintly 
(they thus resemble the nuclei of erythroblasts), and may be surrounded by a special 
covering of hyaline protoplasm. 

(17) The greater part of the protoplasm of the giant cells is coarsely granular, but 
there is a more or less narrow hyaline rim which has a faint but distinct yellow colour 
like that of the perinuclear protoplasm of the erythroblasts, and similar to, only not so 
deep as that of the red blood-corpuscles. 

(18) The giant cells usually possess vacuoles that appear to mark the former position 
of detached nuclear buds. 

(19) The vacuoles situated near the periphery of the giant cell sometimes contain 
erythroblasts. 

(20) The ruptured vacuoles on the surface of the giant cells have the character of 
mouth-like openings, and in them erythroblasts are frequently lodged. 

(21) The giant cells probably never contain non-nucleated red blood-corpuscles. 

(22) The giant cells often enter the splenic vein along with the proper corpuscular 
elements of the blood. 

(23) They occur in the follicles, and some apparently pass into the pulp from the 
follicles. 

(24) In the pulp they are often contained in cell spaces formed apparently by 
connective tissue strands, and it is possible that these cell spaces persist, after the 
disappearance of the giant cells, as the blood spaces of the pulp. 

(25) It is probable that the giant cells are not phagocytes, but that they are 
producers of erythroblasts. 

(26) The special multinucleated vacuolated cells were found in the spleen of an 
eight months' human foetus. 

(27) They are apparently derived from giant cells whose nuclei have become 
isolated, and inclosed each in a vacuole or capsule-like nuclear space. 

(28) In the larger cells a few of the superficial vacuoles alone are empty; in the 
smaller a few only of the vacuoles contain nuclei. 

(29) After all the nuclei except one or two have disappeared from the vacuoles 



296 DR A. J. WHITING ON THE 

the cell resembles the special uninucleated vacuolated cells. Thus the multinucleated 
vacuolated cell seems to afford a connecting: link between the uninucleated vacuolated 
cell and the giant cell. 

(30) The special uninucleated vacuolated cells were found in the spleens of the 
rabbit, rat, guinea-pig, human foetus (at the seventh and at the eighth month), and 
child. 

(31) They appear to be produced from larger or smaller giant cells, by the extrusion 
of nuclear buds, the number of vacuoles increasing until there is little of the original 
protoplasm left, and the amount of nuclear substance gradually diminishing. 

(32) It is doubtful whether these cells ever contain non-nucleated red blood 
corpuscles ; but erythroblasts are occasionally seen within their vacuoles. 



PART II. 
On the Physiology of the Spleen and Blood Formation. 

Chapter V. 

Foa and Salvioli # have shown that the nucleated red cells in the embryonic 
liver bear a direct numerical relation with the erythroblasts and with the giant cells 
in that blood-forming organ ; they have given reasons for believing that the erythro- 
blasts are developed from the giant cells, or, as they term them, hsematoblasts ; and 
they have observed similar cells, affording evidence of a similar process, in the fcetal 
spleen and lymphatic glands. 

As regards the spleen, we have, we think, already produced confirmation of the 
probability of the truth of the theory that its giant cells produce erythroblasts. 

If the endogenous development of erythroblasts within giant cells is an important 
mode of blood production, one would not unreasonably expect to find the mother 
cells in those positions where blood formation is known to be actively progressing. 

The positions in which mammalian blood formation is known to occur may be 
summarised as follows : — 

(a) In the vascular area of the fcetal membranes. 
(/>) Within the foetus during early intra-uterine life. 

(1) In the liver. 

(2) In the subcutaneous connective tissue. 
(c) During late intra-uterine life. 

(1) In the spleen. 

(2) In the bone marrow. 

(3) In the lymphatic glands. 

* Foa and Salvioli (38), p. 125. 



i 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 297 

(d) In early extra-uterine life. 

(1) In the spleen. 

(2) In the bone marrow. 

(e) In adult life. 

(1) In the bone marrow. 

In each one of these situations, at the time when blood formation is known to occur 
in it, the presence of giant cells has been demonstrated. 

Blood formation in the vascular area is associated with mesoblastic cells, con- 
taining a central ball of nuclei — the vaso-formative cells of Ranvier.* Similarly, 
large multinucleated cells or hsematoblasts have been described by WissozKYt in 
the allantois of the embryo rabbit ; and they are considered by him to produce 
small uninucleated hsematoblasts — the erythroblasts — by a process of endogenous 
formation. 

In the liver of the three months' human foetus, Neumann,! m 1874, described 
appearances of the giant cells which, as he believed, indicate an endogenous develop- 
ment of nucleated red blood-corpuscles within them — the mother cells. He also 
alludes § to similar observations by Reichert, who found in the fcetal liver of the 
hen " mother cells filled with a younger generation." Recently, an able paper has 
been published by Omer Van der Stricht,|| on the development of the blood in 
the embryonic liver, in which he states that giant cells appear in the liver at the 
moment when the organ partakes actively in the formation of red blood-corpuscles, 
and accounts for the presence of the nuclei of erythroblasts within the giant cells 
on a theory of phagocytosis. 

The presence of large multinucleated vacuolated cells, tinted with haemoglobin, in 
the subcutaneous connective tissue, was first described by E. A. Schafer IT in the newly 
born rat. Within them he described the formation of non-nucleated red blood-corpuscles. 
If, as would appear from his description, he examined these cells in the fresh condition 
only, and without staining, the newly formed red blood-corpuscles may have contained 
nuclei that were not revealed. 

Giant cells in the bone-marrow were first described by Bizzozero ; '** and in the liver 
and spleen by Kolliker and REMAK.tt The mode of production of red blood-corpuscles 
from giant cells in the embryonic liver, spleen, and lymph glands, and in the adult bone- 
marrow, according to the view advanced by Foa and Salvioli, is described by Bizzozero $ 
as follows : — From the nuclear heap of the giant cell a bud springs ; this, after it has 
increased in size, becomes isolated, makes its way to the periphery of the cell, where it is 
surrounded by a layer of hyaline substance derived from the protoplasm of the giant cell, 
and forms a projecting bud on the surface of the cell ; it ultimately becomes detached as 

* Ranvier (45), p. 640. f Wissozky (42), p. 479. 

X Neumann (28), p. 469. § Neumann (28), p. 448. 

II Van der Stricht (48), p. 60 and p. 88. 1" Schafer (35), p. 243. 

** Bizzozero (31), p. 30. tt Remak (27), p. 99. 
\\ Bizzozero (31), p. 30. 



298 DR A. J. WHITING ON THE 

a small daughter cell, consisting of a nucleus enveloped in a layer of hyaline substance, 
that later becomes coloured with haemoglobin, and so an erythroblast is formed. In one 
respect only I differ from this view, as I believe that the perinuclear protoplasm of the 
erythroblast is, in the spleen, tinted with haemoglobin before the cell escapes. Alluding 
to these observations, which are practically the same as Neumann made on the giant 
cells of the liver, Bizzozero * remarks that the usual association of giant cells with 
nucleated red blood-corpuscles, pointed out by Foa and Salvioli, affords only presumptive 
evidence in favour of their view, and that it would have been much more convincing 
if one had seen, what he believes none has ever seen, the protoplasm of the giant cells 
coloured with hgemoglobin, or the nucleated red cells already coloured while attached to 
the giant cells. Both of these phenomena we are able, as we believe, to demonstrate. 

A case of Leucocythsemia, recorded by Dr Robert MuiR,t the spleen from which I 
examined, has a special interest with reference to blood formation. Blood taken from the 
finger, on many occasions during life, always showed large numbers of nucleated red cells. 
The spleen was much enlarged, but the bone-marrow and liver were unaffected. 

The Spleen contains numerous giant cells (about twenty or thirty in a section half-an- 
inch square), very numerous erythroblasts and nucleated red blood-corpuscles, and large 
numbers of special uninucleated vacuolated cells like those in the spleen of the child. 
The giant cells have the ordinary characters, — coarsely granular protoplasm, a central 
nuclear heap, vacuoles, mouth-like openings, many of which contain erythroblasts. Their 
average measurement is probably about 40 v by 20 m. Occasionally the central nuclear 
heap is circumscribed by a regular outline, but usually it gives off pyriform or Indian 
club-shaped buds. (Plate III. fig. 22.) The buds vary much in size, but in the largest 
the head of the club is as large as an erythroblast, and often it is seen to be contained 
in what appears to be a perinuclear space. Frequently an erythroblast is seen to be 
connected with the giant cell by the stalk of the pyriform nucleus, attached to the 
central nuclear heap, and by a pedicle of protoplasm apparently continuous with the 
protoplasm of the giant cell. 

The mediastinal lymph glands were greatly enlarged, but they contained no giant 
cells, and few, if any, nucleated red cells or erythroblasts. Thus it is probable that the 
nucleated red cells found in the blood had their origin in the spleen. 



On Artificial Ansamia in Dogs. 

The following is a precis of the experiments of Bizzozero and Salvioli,^ which prove 
the frequent occurrence of nucleated red cells in the spleens of dogs that have been 
rendered anaemic. 

* Bizzozero (31), p. 32. + Mum (47), p. 480 (Case 54). 

| Bizzozero and Salvioli (30), p. GOO. 



COMPAKATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 



299 



No. of 
Experiment. 


Haemorrhage, percentage of body 
weight. Days' interval. 


Hemoglobin fell to 


Result on Spleen as regards 
Nucleated Red Cells. 


I. 


2*9 per cent. 

Two days. 
3*7 per cent. 

Three days. 


43 - 5 per cent. 


Very numerous. 


II. 


3*94 per cent. 

Four days. 


58 - 4 per cent. 


Sparse. 


III. 


3-7 per cent. 

Three days. 
2-6 per cent. 

Six days. 
1*1 per cent. 

Two days. 


40 per cent. 


Moderate numbers. 


IV. 


3 per cent. 

Four days. 

2 - 48 per cent. 

Four days. 


46 per cent. 


Sparse. 


V. 


1*73 per cent. 

Five days. 
2*08 per cent. 

Two days. 


45 per cent. 


Extremely large numbers. 


VI. 


1*52 per cent. 

Ten days. 


62 per cent. 


None. 


VII. 


2 # 98 per cent. 

Four days. 
3-21 per cent. 

Five days. 
2 14 per cent. 

Three days. 


58'2 per cent. 


Considerable numbers. 


VIII. 


3 per cent. 
Four days. 
2 - 55 per cent. 

Two days. 

2-1 per -cent. 

Two days. 


42 - 7 per cent. 


A few. 


IX. 


3-5 per cent. 

Four days. 

3 per cent. 

Five days. 
2*85 per cent. 

Four days. 

3*1 per cent. 

Six days. 
2-78 per cent. 

Five days. 
2-44 per cent. 

Four days. 


257 per cent. 


Enormous numbers. 



300 



DR A. J. WHITING ON THE 



No. of 


Hemorrhage, percentage of body 


Haemoglobin fell to 


Result on Spleen as regards 


Experiment. 


weight. Days' interval. 


Nucleated Red Cells. 


X. 


2-3 per cent. 

Seven days. 
3 per cent. 
Three days. 
3 per cent. 
Two days. 
3 per cent. 








Three days. 


39 per cent. 






Three days. 




Great numbers. 



They describe the naked eye appearance of the spleen after copious haemorrhage as 
characteristic ; it is rose-coloured and much swollen. While they examined the splenic 
pulp microscopically in the fresh condition, both with and without indifferent fluids, 
they apparently attended to the nucleated red cells alone, and they do not record any 
examination of sections of the spleen. 

Dr Eobert Muir # produced anaemia in three dogs, and observed especially the 
accompanying changes in the red bone-marrow. He was good enough to give me the 
spleens of these dogs for microscopic examination, and the following is a summary of his 
observations that bear especially on that examination. 



No. of 
Experiment. 


Haemorrhage, per- 
centage of body weight. 
Days' interval. 


Result on Blood. 


Result on Spleen ; 

Nucleated Red 

Corpuscles. 


1. No. of Red 
Corpuscles. 


2. Nucleated Red Corpuscles. 


I. and III. 


2 per cent. 

Seventeen days. 

2*5 per cent. 

Six days. 
2-3 per cent. 

Three days. 
2*3 per cent. 

Eight days. 

On 3rd day. 

On 8th day. 


(7,460,000) 

2,884,000 
4,280,000 


None. 
Present during last 1 2 days. 


A few. 


II. 


2-8 per cent. 

Four days. 

2*5 per cent. 

Nine days. 
On 3rd day. 
On 9th day. 


(6,098,000) 

2,451,000 
3,311,000 


Present during last 11 days. 


A few. 


IV. 


2*85 per cent. 

Four days. 
2-5 per cent. 

Nine days. 
On 2nd day. 
On 9th day. 


(5,830,000) 

2,555,000 
3,379,000 


Present during last 9 days. 


Present. 



* Mum (47), p. 491. 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 301 

With regard to Dr Mum's estimate of the number of nucleated red cells in the spleen, 
obtained by examining a scraping of its surface, it must be borne in mind that such 
a preparation contains elements derived from other sources than the pulp (those from 
the follicles being in great numbers), and cannot, therefore, be fairly compared with 
a fresh preparation of bone-marrow, that corresponds, practically, solely with the 
pulp. 

In the Spleen of the Dog from Experiment II. there are large numbers of giant 
cells, — on a rough computation about 1000 in each section through its thickest part. 
They present the usual characters, but their outline shows an unusually large number of 
mouth-like openings. Their nuclei exhibit much budding ; perhaps the most frequent 
arrangement is a rosette of pyriform buds. A few cells show karyokinetic figures. 
There were no giant cells observed within the follicles. (Plate III. fig. 23.) There are 
enormous numbers of erythroblasts and nucleated red cells present, many of the former 
being clustered around the giant cells. There were very many more nucleated red cells 
and erythroblasts in the blood of the splenic vein than in that of the artery. The 
protoplasm, both of the giant cells and of the erythroblasts, has a marked yellow colour. 
A few eosinophilous cells are present in the pulp. 

In the Spleen of the Dog from Experiments I. and III. there are equally large 
numbers of giant cells — about 1000 in a section. Their outline has fewer mouth-like 
openings (than in Expt. II.), but their nuclei show similar budding. The typical 
arrangement is a rosette of pear-shaped nuclei, their apices, which point inwards, being 
frequently connected together ; occasionally a single cell has two such rosettes, one 
arranged around each end of a somewhat thick stem. Rarely a giant cell may be seen 
within a follicle. Almost all the cells in the follicles are leucoblasts, and this fact, 
together with the presence of numerous giant cells in the pulp, remind one of the appear- 
ances in the spleen of the young Mammal. There are very large numbers of erythro- 
blasts and nucleated red cells, but not so many as in the previous spleen ; and there 
is a comparatively small number of these cells in the veins. Pigment-holding cells are 
present in large numbers, and also globular masses of free, or apparently free, pigment. 
Eosinophilous cells were not found. A considerable amount of a coarsely granular sub- 
stance was seen in the veins, some of it collected into round clumps, and some of it in 
the form of discrete coarse granules ; as it so nearly constantly occurs in the veins in 
association with the giant cells in the pulp, it is suggestive that it may possibly result 
from the breaking down of the inner coarsely granular portion of the protoplasm of the 
giant cells. 

In the Spleen of the Dog from Experiment IV., the most striking naked-eye 
character of which is its pale lemon-yellow colour, there are considerable numbers of 
giant cells, but not so many as in the other two spleens — numbering, on a rough 
estimate, about 500 in a section. This spleen is smaller than the other two, and the 
body-weight of the dog from which it was obtained was a third less. 

Many of the giant cells are smaller — only about half the average size of those in the 

VOL. XXXVIII. PART II. (NO. 8). 2 S 



302 DR A. J. WHITING ON THE 

other two spleens. They have a more irregular surface than those of the spleen imme- 
diately preceding, and about the same as in the spleen of Expt. II. Their protoplasm 
shows a conspicuous division into hyaline rim and coarsely granular core. They were 
seen a few times within follicles, frequently in the veins within the spleen, and one was 
seen in the peripheral blood-sinus of an ellipsoid. There are present in the pulp enor- 
mous numbers of mature nucleated red cells, but a comparatively small number of ery- 
thro blasts. Occasionally a nucleated red cell may be seen to have two nuclei. A large 
number of nucleated red cells, in different stages of maturity, are seen within the veins. 
Many coarsely granular protoplasmic corpuscles are present ; they are grouped in the 
follicles as in the spleen of the child, and are scattered throughout the pulp, but are 
especially numerous in the neighbourhood of the follicles. As regards their general 
characters, they may be compared with small uninucleated giant cells. They sometimes 
show karyokinetic figures. Some of the larger are vacuolated, and resemble the special 
uninucleated vacuolated cells characteristic of the spleen of the child. There are a few 
eosinophilous cells and a few pigment-holding cells present ; the latter are mainly in the 
follicles. Scattered throughout the pulp are large numbers of small lymphoid cells, or 
uninucleated leucocytes. The germinal centres of the follicles are relatively small, and 
there are many small lymphoid cells scattered among its leucoblasts. 



Tivo Experiments on Anaemia in Dogs. 

In following up the indications obtained from the evidence detailed up to this point, 
I bled two dogs, with a principal object of examining the giant cells, that I expected to 
make their appearance as a result of the bleeding, in the fresh condition. Both experi- 
ments were on adult fox-terriers, and they were conducted as nearly as possible in the 
same way. The dogs were put on a fixed diet, and their blood was examined at the same 
hour each day, and with the same time relation to feeding. When the observations 
were constant, the same, or nearly the same, percentage of the body weight of blood was 
removed in each case by incising the external jugular vein. Ether was used as an 
anaesthetic. A curious fact was noticed in each bleeding — that the last portion of blood 
withdrawn clotted immediately it passed from the vein into the cannula, so that the 
latter became blocked. The routine followed in the examination of the blood was as 
follows : — The interior of the lobe of the ear was cleansed, and a small incision was made 
with a sharp scalpel ; the number of the corpuscular elements was estimated by means of 
the Thoma-Zeiss haemocytometer, diluting the blood with methyl salt solution ; the per- 
centage of haemoglobin was estimated with Gowers' haemoglobinometer ; and the specific 
gravity was ascertained by Haycraft's method ; cover glass films of blood were dried 
in the air and afterwards stained, and fresh preparations of blood were made by 
allowing a drop to be spread in a thin layer on a slide by the weight of a cover glass 
and ringing the cover glass with oil. The wounds of the operations were treated 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 303 

antiseptically, and, except in one case, healed by first intention. After each operation, 
two pints, or more, of milk were given immediately, and as much water as the animal 
desired. 



Experiment I. — Part I. 



Day of 
Experiment. 


Specific 
Gravity. 


Per Cent. 
Hb. 


Red Corpuscles. 


Leucocytes. 


Nucleated 
Red Cells. 


Weight 
in Kilo. 


1 


1057 


72 


6,590,000 


11,000 


None. 


6-5 


3 


1058-3 


72 


6,640,000 


12,000 


?> 




5 


1059 


72 


6,680,000 


12,000 


3J 


6 ; 6 


7 




Blood 


abstracted, 2*4 p 


er cent, of b 


ody weight. 




Four hours later. 


1049 


60 


4,880,000 


36,000 


None. 


6-47 


8 


1053 


60 


5,840,000 


34,000 


>) 


)) 


9 


1054-5 


60 


4,330,000 


15,000 


)> 




10 


1054-2 


62 


5,210,000 


16,000 


s> 




12 


1053 


58 


5,640,000 


20,000 


>> 




14 


1053-3 




5,135,000 


16,000 


)) 


6-47 


16 


1053-3 


54 


5,080,000 


18,000 


)! 




19 


1055-7 


54 


4,987,000 


20,000 


>> 


6-5 


20 




Bloo 


d abstracted, 3 pe 


r cent, of bo 


dy -weight. 




21 


1050 


38 


3,560,000 


32,000 


Very few (4J. 


6-5 


22 


1050 


36 


3,057,000 


32,000 


Few (30). 


... 


23 


1050 


38 


3,720,000 


28,000 


Few (20). 




24 


1050 


38 


3,900,000 


26,000 


Very few (5). 




26 


1051 


40 


3,760,000 




None. 


6-7 


28 


1050 


40 


3,960,000 


26,000 


j) 


... 


30 


1051-2 


40 


4,040,000 


16,000 


>> 





Note. — The figures in the column " nucleated red cells " indicate the average number of cells seen in single films 
{\ means one in four films). 

There were no poikilocytes observed at any time ; but on the 10th day, three days 
subsequent to the first bleeding, and afterwards, the red corpuscles varied in size slightly, 
a few being 5, 6, or 7 p. 

On the 2lst day, the day following the second bleeding, the red blood-corpuscles 
showed a slight tendency to invagination ; and nucleated red cells were seen for the 
first time during the experiment, one or two being found after careful search through 
several films. 

On the 22nd day, in a plain preparation of blood, there were seen several large cellular 
bodies, one much larger than the others, which seemed to be giant cells. The largest cell 
was much lobed, large buds projecting from its surface in all directions, giving an 
appearance like that described in the giant cell of the spleen of the mouse, when 
examined fresh in methyl salt solution. A small round cell was in contact with the 
large cell, but apparently detached from it. The peripheral part of the protoplasm of the 
large cell was tinted yellow here and there, as also was the whole of the protoplasm of 
the small cell, and the latter seemed to contain a round nucleus. As the blood- 
corpuscles ran together, other large cells were revealed, lying in spaces comparatively free 



304 



DR A. J. WHITING ON THE 



from red cells. One special cell, somewhat smaller than the average, did not possess any 
buds, but the nuclei were visible grouped in a heap in the middle of the cell, and were 
surrounded by a comparatively narrow band of hyaline protoplasm which reached to 
the periphery, and had a deep yellow colour. The fresh preparations showed a very 
rich felt work of fibrin and very many blood plates, mostly in clusters. The films 
contained several nucleated red cells, perhaps about thirty in each. Their protoplasm 
stained more deeply with methyl blue than that of the majority of the non-nucleated 
forms. Some of the latter, however, as Mum has recorded, show a similarly deep 
staining, with an irregular surface as if of softer consistence than the majority, 
suggesting that they had recently been in the nucleated condition. 

On the 23rd day several large cells were seen in a plain preparation of blood. The 
nucleated red cells were not so numerous as on the preceding day, perhaps about twenty 
in a film. Blood plates were very numerous. 

On the 2Uh day one large special cell was seen in one of two plain preparations 
of fresh blood. There was a marked reduction in the number of nucleated red cells ; 
about five were seen in each film. The red blood-corpuscles varied much in size. 

On the 26th day there were no large cells seen in several plain preparations of 
blood. The nucleated red cells had apparently also disappeared ; but the films contained 
many darkly stained softer red corpuscles. 

Between the second bleeding and the third an interval of forty-two days was 
allowed to elapse. 

Experiment I. — Part II. 



Day of 

Experiment. 


Specific 
Gravity. 


Per Cent. 
Hb. 


Red Corpuscles. 


Leucocytes. 


Nucleated 
Red Cells. 


Weight 
in Kilo. 


1 
2 
3 
6 


1052-2 

1052-2 
1052-2 


54 

54 

54 


5,740,000 
5,840,000 
5,893,000 
5,866,000 


18,000 
14,000 
16,000 
14,000 


None. 
None. 


6-6 
6-6 


7 




Bloo 


d abstracted, 3 pe 


r cent, of bo 


dy weight. 




8 

9 

10 


1050-8 
1050-5 
The 


38 

40 

dog was k 


4,046,000 

4,120,000 

illed with chlorofo 


28,000 
11,000 
rm. 


None. 


6-4 



Note. — Day 1 of part 2 corresponds with day 56 of part 1. 



On the three days before the last bleeding, large special cells were found in the blood, 
on an average one in a preparation. 

On the 8th day, the first day after the bleeding, in six plain preparations (four of 
which were examined on Schafer's warm stage) there were seen many large cells, about 
thirty or forty in each. Some were found in the hamiocytonieter preparation : one was 
seen to occupy about the half of a ruled square. This had a blue-stained central portion 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 305 

and a yellow periphery ; in the middle of the cell, oval outlines were visible, apparently 
those of nuclei, and on its surface were several blunt processes or buds. Most of the 
other special cells were smaller, about eight times the size of a red blood-corpuscle. 
In a preparation made with methyl salt solution and osmic acid several special 
cells were seen ; one was very large, markedly yellow, and covered all over with 
buds. 

On the warm stage they exhibited amoeboid movement at their periphery in a 
specialised rim of the protoplasm. In one instance there was seen a bud, containing 
what seemed like a rounded collection of very coarse granules, an appearance probably 
due to the nodes of an intranuclear network, which became detached so as to form 
a small round cell. In one of the large cells vacuoles were observed, and in several, 
creek-like fissures were seen in their outline. Neither the red blood-corpuscles nor the 
leucocytes showed any tendency to adhere to the surface of the large cells. There was 
a very rich felt work of fibrin in the plain preparations. 

Nucleated red cells were not found in the films of blood. 

On the morning of the 9th day the blood contained very many large cells, on a 
rough estimate about forty or fifty in a preparation. They have a characteristically 
hyaline and glittering surface, characters more marked than of the somewhat similar 
surface of the leucocytes, and quite unlike those of the surface of the clumps of blood 
plates. In one case a pear-shaped bud was connected with a large cell by its long pedicle 
that was contained in a kind of channel in the protoplasm of the large cell ; the pedicle 
was seen to give way, and there was left a small round cell, with a coarsely granular 
centre, lying in a depression on the surface of the large cell. Two similar small cells 
were seen in one instance to come into apposition with a large cell, but almost 
immediately thereafter they became again widely separate. The nuclei of the small 
cells show the remarkable dotted appearance to which reference has been made, and 
each is surrounded by a narrow rim of hyaline amoeboid protoplasm. There was seen a 
very strong fibrin network. 

On the afternoon of the same day (9th) the number of large cells in the blood was 
very much reduced. There were no nucleated red cells found in the blood on this 
day. 

It is difficult satisfactorily to explain the absence of nucleated red cells from the 
blood, if it be considered that the small cells, which are budded off on the warm stage 
from the large cells, are probably erythroblasts. These large cells are in abnormal 
conditions, and it may be that contact with the glass, together with the heat, may have 
precipitated the detachment of buds or accelerated a process that normally occurs 
slowly. 

On the 10th day the dog was killed with chloroform. 

The Spleen measured A\ inches in length and weighed 1 3 grammes ; it w T as of a dark 
red colour ; it was slightly soft and rather full of blood. A scraping of its surface was 
examined in methyl salt solution, and, after dilution with hydrocele fluid, preparations 



:50G DR A. J. WHITING ON THE 

were examined on the warm stage. Erythro blasts and nucleated red cells in fairly 
large numbers and a few giant cells were recognised in all the fresh preparations, and 
also in films of the pulp fixed in saturated solution of corrosive sublimate and subse- 
quently stained. The giant cells in the fresh preparations were hyaline in appearance 
and much budded, like those of the blood ; but amoeboid movement was not observed 
in any of them on the warm stage. 

Sections of the Spleen showed comparatively few larger giant cells, perhaps about 
sixty in each ; and they do not exhibit the appearances characteristic of active change. 
There are smaller giant cells present in considerable numbers ; they are as a rule nearly 
round, and have a small and but little lobed nuclear heap. The larger giant cells have 
an unusually distinct perinuclear space. A giant cell and a few coarsely granular 
protoplasmic corpuscles are occasionally seen in the follicles. There is a very small 
number of erythroblasts and of nucleated red cells, but they are apparently almost, if 
not quite, as numerous in j)roportion to the number of giant cells as in the other spleens. 
There was seen in the veins a very small number of nucleated red cells. A few 
pigment-holding cells were found in the follicles, and numerous pigment masses in the 
pulp. 

TJie Bone-Marrow as seen in fresh preparations contained many erythroblasts, 
nucleated red cells, and giant cells. The marrow of the ribs contained proportionately 
more of these cells than that of the femur, indeed it seemed to be composed entirely of 
them, and could be readily squeezed out from the cavity of the rib as a thin fluid. The 
giant cells appeared to be less hyaline than those of the blood and spleen, and to have 
fewer buds. Amoeboid movement on the warm stage was not seen. Sections of the 
bone-marrow of the femur show numerous giant cells, on a rough estimate about 
150 in each section. The yellow colour of their protoplasm is nearly as deep as that 
of the red blood-corpuscles. A few grains of pigment are scattered here and there. 
Very many erythroblasts and nucleated red cells are present, far more in proportion 
to the number of giant cells than in any spleen I have examined. 

In a Lymphatic Gland taken from the neck there are a few erythroblasts and 
nucleated red cells which appear to be colourless. There are a few somewhat large 
multinucleated protoplasmic cells, like small giant cells, perhaps one or two in a section. 
In the sinuses are large numbers of coarsely granular, uninucleated, protoplasmic 
corpuscles that stain somewhat deeply with eosine ; their average size is about 10 m. 
There are numerous pigment-holding cells present. 

In a Mesenteric Lymphatic Gland there arc erythroblasts in small number. In the 
sinuses there are in addition numerous uninucleated vacuolated cells like those 
characteristic of the spleen of the child ; and there are cells without vacuoles but 
otherwise similar. 

Films of the blood taken from the splenic vein while the dog was dying did not 
contain any nucleated red cells. 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 



307 



Experiment II 



Day of 

Experiment. 


Specific 
Gravity. 


Per Cent. 
Hb. 


Bed Corpuscles. 


Leucocytes. 


Nucleated 
Red Cells. 


Weight 
in Kilo. 


1 


1059-5 


84 


6,670,000 


7,000 


None. 


8-6 


2 


1059 


84 


6,740,000 


8,000 


)! 




3 


1058-5 


84 


6,780,000 


6,000 


)) 


8 : 6 


4 




Blood 


abstracted, 2-4 p 


er cent, of b 


ody weight. 




Three hours later. 


1054-5 


72 


5,613,000 


30,000 


None. 


• 8-4 


5 


1055 


72 


5,960,000 


10,000 


j) 


... 


7 


1055 


70 


6,250,000 


20,000 


; j 


... 


9 


10545 


72 


6,300,000 


20,000 


)j 


8-2 


11 


1057 


72 


6,140,000 


15,000 


)) 


... 


14 


1057 


74 


6,413,000 


12,000 


)) 


8-4 


15 




Blood 


abstracted, 3-2 p 


er cent, of b 


ody weight. 




16 


1052-2 


62 


5,020,000 


28,000 


None. 


8-4 


17 


1051-2 


56 


5,400,000 


30,000 


Few (10). 




18 


1053 


60 


5,440,000 


14,000 


Few (20). 




19 


1053-3 


58 


4,950,000 


14,000 


Very few (5). 


... 


21 


1054-5 


58 


5,090,000 


12,000 


None. 


8-2 


22 




Bloo 


d abstracted, 3 pe 


r cent, of bo 


dy weight. 




23 


1050-5 


48 


4,160,000 


54,000 


Few (10). 


8-2 


24 


1051-2 


48 


3,640,000 


86,000 


Numerous (40). 




25 


1051-2 


48 


4,030,000 


30,000 


Few (15). 




26 


1051-2 


48 


4,067,000 


16,000 


Very few (3). 


8-3 


28 


1051-2 


48 


4,060,000 


8,000 


Very few (2). 




29 


The 


dog was k 


illed with chlorofo 


rm. 







Poikilocytosis was never seen during this experiment, neither any tendency to 
invagination of the red blood-corpuscles ; and there was very little variation in the size 
of the red blood-corpuscles at any time. 

On the 17 th day, two days after the second bleeding, nucleated red cells were found 
in the films for the first time, about ten in each. There were many more deeply 
stained, non-nucleated red corpuscles with an irregular surface. 

On the 18th day several large cells were seen in a plain preparation of blood. Their 
coarsely granular protoplasm had a faintly yellow tint. A somewhat small one (24 /* 
in diameter) was noticed to have a rounded bud (8 n*) projecting from its surface, the 
protoplasm of which was markedly yellow. Nucleated red cells were in larger numbers 
than on the previous day, about twenty in a film. The blood plates were very numerous, 
and the plain preparations showed a rich fibrin network. 

On the 19th day there were no large cells found in the blood, and only a few 
nucleated red cells in the films, about five in each. 

On the 21st day there were no large cells found and no nucleated red cells, but 
there were many softer, more deeply stained red blood- corpuscles. 

On the 23rd day, the first day after the third haemorrhage, large cells were not found 
in six plain preparations of blood. A remarkable phenomenon was the very large 



308 DR A. J. WHITING ON THE 

number of leucocytes, there being one uninucleated to three multinucleated. About 
ten nucleated red cells were found in each film. 

On the 2ith day three or four large cells were found in four preparations. One cell 
was seen under the microscope on the warm stage about two minutes after it was 
removed from the body ; in it a coarsely granular core of protoplasm was surrounded by 
a rim of yellowish finely granular almost hyaline protoplasm, that showed active amoeboid 
movement. In the rim were several rounded projections, four of which were seen to 
become detached as small round cells. Nucleated red cells are fairly numerous in 
the films, about forty in each. Their perinuclear protoplasm is in smaller amount than 
usual and apparently also softer, as the outline of the cell is nearly always irregular, 
while that of the red corpuscles is regular. Many red corpuscles stain more deeply than 
the rest, and some only of these have an irregular surface. 

On the 25th day one large cell was seen in seven preparations. Nucleated red cells are 
less numerous than in the films of the previous day ; about fifteen were seen in each film. 

On the 26th day two large cells were seen in two preparations of blood, one in each. 
The one cell measured 26 m by 11 m, and from one side of it there projected a nucleated 
bud, 10 im in diameter. The whole cell had a yellow tinge. Only two or three 
nucleated red cells were found in a film. 

On the 28th day one or two nucleated red cells were found in each film ; and two 
plain preparations of blood showed two large cells, somewhat below the average size. 

On the 29th day the dog was killed. 

Tlie Spleen was 3|- inches in length and weighed 16 '7 grammes. It was of a dark 
red colour, of firm consistence, and was not very vascular. Fresh preparations and films 
showed several giant cells and a fairly large number of nucleated red cells and erythro- 
blasts ; all these kinds of cells were distinctly more numerous than in similar preparations 
of the previous spleen. Amoeboid movement was not seen in the giant cells, which were 
examined in aqueous humour on the warm stage. 

(Preparations of the Bone-Marrow showed numerous giant cells ; but none were seea 
in films made from the Lymph Glands.) 

In sections of the Spleen there was seen a comparatively small number of giant cells, 
on a rough computation about 250 in each. They have the ordinary characters of giant 
cells in a not very active condition, that is, their nuclei show little budding and there are 
relatively few mouth-like openings at their surface. The knobs projecting from the 
central nuclear heap are sometimes seen to be the rounded ends of short thick pyriform 
buds. Their protoplasm has a well marked yellow tint. There are considerable numbers 
of erythroblasts and nucleated red cells in the pulp, by no means so many as in the 
spleens of the three former dogs, but more numerous than in the immediately preceding 
spleen. There occur in the veins not a few nucleated red cells. The follicles, whose 
germinal centres are relatively large, contain a considerable number of pigment-holding 
cells, but there is little pigment in the pulp. Occasionally a protoplasmic knob of a 
giant cell, and sometimes an erythroblast, has the colour of pigment, due probably to 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 309 

a post-mortem change. We think it likely that the latter appearances are due to 
similar causes to those which produce a pigmented zone under the capsule of any 
spleen that is exposed to the drying influence of the air before hardening. 

In the Bone-Marrow of the femur there are fairly large numbers of giant cells, 
perhaps about 120 in a section. But they are by no means so close together as in the 
spleens of some young Mammals, nor in the spleen of the adult hedgehog. Their average 
size, too, seems to be rather smaller : one of the largest measured 34 by 20 /*, while the 
average diameter seems to be about 20 /*. Their characters are apparently identical with 
those of the cells found in the spleen. There are many small giant cells present whose 
protoplasm stains faintly blue with haematoxylin. Erythroblasts and nucleated red 
cells occur in large number ; their perinuclear protoplasm has a distinctly yellow 
tinge ; their nuclei occasionally show karyokinetic figures, — the nuclei at any rate of 
the erythroblasts, — as do also the nuclei of the giant cells. There are numerous 
eosinophilous cells present. 

In a Lymphatic Gland taken from the neck there are apparently no giant cells, but 
there are a few erythroblasts and nucleated red cells, and eosinophilous cells, and fairly 
numerous pigment cells and coarsely granular protoplasmic corpuscles, all contained in 
the medullary sinuses of the gland. 

In a Mesenteric Lymph Gland there are a few somewhat small giant cells, whose 
average diameter is about 20 j<*. Their protoplasm is rather finely granular, and stains 
only faintly pink with eosine. The nuclei are sometimes arranged in a ring, midway 
between the centre and the periphery of the cell, but sometimes they nearly fill the 
whole cell. Occasionally the giant cells have vacuoles. Erythroblasts and nucleated 
red cells are numerous ; the perinuclear protoplasm of both stains faintly, if at all, 
with eosine, and seems to be practically destitute of haemoglobin. There are a few 
coarsely granular protoplasmic corpuscles present, some of which are vacuolated, and 
numerous pigment-holding cells. 

Results of Experiments. 

It seems, therefore, that upon the induction of the anaemic state in dogs the spleen 
reverts to its early condition, that characteristic of early extra-uterine life. And the 
number of giant cells in the spleen appears to vary directly with the number of erythro- 
blasts and nucleated red cells in it, and to some extent with the number of nucleated 
red cells in the blood ; but giant cells may be present in the spleen without any nucleated 
red cells occurring in the blood of the splenic vein. 

In my experiments the spleen was not found to be remarkably swollen, or to have 
the rose-pink colour described by Bizzozero and Salvioli ; but the spleens of Dr Muir's 
experiments were much more swollen, and it seems probable that those appearances 
co-exist with the higher degrees only of haematopoietic activity. 

That many nucleated red blood-corpuscles are found in the red bone-marrow, and 

VOL. XXXVIII. PART II. (NO. 8). 2 T 



310 DR A. J. WHITING ON THE 

comparatively few in a similar mass of the splenic pulp, seems to me to be insufficient 
ground for concluding that blood formation is more active in the former than in the 
latter, for the cells of the pulp in all probability reach the blood stream much more 
easily and rapidly than do those of the marrow ; the spleen has a very large and free 
blood supply, while the bone-marrow has a comparatively poor blood supply ; the splenic 
pulp is surrounded by a contractile and elastic framework, but the red marrow is inclosed 
in a rigid case of bone ; the spleen undergoes rhythmic contraction every minute and 
periodic enlargement during digestion, when the spaces of the pulp may be thoroughly 
flushed out, but, as far as we know, no such change affects the bone-marrow. 



Summary of Effects of Hemorrhage. 

The following are the principal changes that were observed in our experiments as a 
consequence of the abstraction of blood : — 
A. On the Blood : — 

(1) A fall in the number of red corpuscles. 

(2) A fall in the specific gravity. 

(3) A fall in the percentage of haemoglobin. 

(4) An immediate and transient increase in the number of leucocytes. 

(5) A late diminution in the average size of the red corpuscles. 

(6) A transient appearance of giant cells. 

(7) A transient appearance of nucleated red cells. 

(8) An increase in the number of blood plates. 
B On the Spleen : — 

(1) A slight increase in size. 

(2) The appearance of numerous giant cells. 

(3) The appearance of proportionately numerous erythroblasts and nucleated 

red cells. 
The latter two facts afford, we think, strong positive evidence in favour of the view 
that the presence of giant cells is a frequent, if not an invariable, accompaniment of 
blood formation ; and, together with the phenomena exhibited by the giant cells of the 
blood on the warm stage, strongly suggest the probability that the giant cells produce 
erythroblasts in the spleen. 

On Artificial Anemia in the Rabbit. 

But I have some negative evidence to offer, derived from the examination of the 
spleen of an anaemic rabbit. 

Both Neumann and Freyer * and Bizzozero and Salvioli t found that, in rabbits, 

* Neumann (29), p. 446. f Bizzozero (30), p. 599. 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 311 

artificial anaemia does not stimulate the spleen to haematopoietic activity. Muir * pro- 
duced anaemia in two rabbits with similar results. One rabbit was bled to the extent of 
2 "2 per cent, of the body weight ; the red corpuscles fell as low as 2,846,000 from 
6,181,000 ; but nucleated red cells did not appear in the blood, nor did he find any in 
the spleen on examining it in the fresh condition. He was good enough to give me the 
spleen for examination. 

Each Section of the Spleen shows a portion of one or sometimes of two giant cells. 
Erythroblasts and nucleated red cells are present in very small numbers. The follicles 
contain many leucoblasts, and there are numerous small lymphoid cells or uninucleated 
leucocytes in the pulp. Fairly large numbers of coarsely granular protoplasmic cor- 
puscles, some of which are vacuolated, are found in the pulp, and a few in the follicles. 
Numerous pigment-holding cells occur both in the follicles and pulp, and ■ large masses 
of coarse granules are present in the splenic veins. 

These facts tend to show that, if blood formation in the spleen does not follow the 
production of artificial anaemia, the giant cells do not appear in it in any consider- 
able numbers, and that, with few erythroblasts and nucleated red cells in the spleen, there 
are very few giant cells present in it. 

And the occurrence of giant cells in large numbers in the spleen of dogs rendered 
anaemic, and of young animals actively forming blood, cannot, I consider, be explained 
on the theory that the giant cells are phagocytes ; while the fact that I have never found 
red blood- corpuscles within the giant cells is to me negative evidence strongly against 
that theory. 



PART III. 

Methods — Bibliography — Description of Figures. 

Chapter VI. 
Methods. 

The spleens were invariably obtained as fresh as possible. 

Of the three principal methods of hardening employed, that of the Physiological 
Laboratory of the University of Edinburgh has given, on the whole, the best results. 
Small portions of the spleen are placed in methylated spirit for twenty-four hours, then 
in a mixture of Muller's fluid and methylated spirit (in the proportion of three of the 
former to one of the latter by volume) ; the fluid is changed on the fourteenth day ; on 
the twenty-ninth day the tissue is transferred to methylated spirit, previously washed 
well in water to remove the bichromate salt, and after a fortnight in alcohol the tissue 
is ready for section. Flemming's strong solution (chrom-osmic-acetic acid), followed by 
alcohol, gave very good results, but his weak solution produced alteration in some of the 

* Mum (47), p. 497. 



312 DR A. J. WHITING ON THE 

cellular elements. The method of fixing the tissue by a saturated solution of corrosive 
sublimate proved to be very good for the spleen. The solution was sometimes used 
warm, and sometimes 075 per cent, sodium chloride was added. Small pieces of tissue 
were placed in this solution for about half-an-hour, after which they were thoroughly 
washed in water, normal salt solution, or dilute alcohol, and were then taken through 
successive alcohols of increasing strength, and left in methylated spirit until sufficiently 
hardened. 

Sections were made in two ways — after freezing the tissue saturated with gum and 
after imbedding in paraffin. Each was found to be preferable for different purposes ; in 
studying the cellular elements of the pulp, the giant cells were best shown by the gum 
method, and the erythroblasts by the paraffin method. The former was of special service 
in allowing of the detachment of the cellular elements of the pulp from the reticulum. 
We found the gum method the more generally preferable. The method of " shaking " 
the sections was found to be better than that of pencilling them, because it was practi- 
cally impossible to remove the free cells without removing large portions of the stroma 
as well. Sections previously stained were placed in a wide test tube with water or 
normal salt solution, and the tube was gently shaken for about a minute. The sections 
were always broken up into several pieces of varying size, and this was advantageous, 
as the reticulum was revealed best near the free edges of such small pieces. 

In staining the sections, no method proved so valuable as that of using hgematoxylin 
followed by eosine. Sections were placed in a solution of the former, in the strength 
of one to twenty of distilled water, for about ten minutes ; they were then washed in 
distilled water and allowed to remain in a 1 in 2000 watery solution of eosine for two 
or three minutes. The eosine was of special use in acting as an energetic stain for 
protoplasm containing haemoglobin. Picric acid in saturated alcoholic solution was 
sometimes used instead of eosine. Ehrlich's acid hsematoxylin gave good results. 
Ehrlich-Biondi's triple stain, of methyl green, acid fuchsine, and orange, was occa- 
sionally used, but was of no special advantage. The sections were sometimes mounted 
in Farrant's solution, but generally in Canada balsam. 

The splenic tissue was often examined in the fresh state, sometimes in the form of 
a simple scraping, but usually diluted with a normal salt solution tinted by methyl 
blue. Portions of scrapings diluted with aqueous humour or hydrocele fluid were 
placed between cover glasses, rung with oil and examined on Schafer's warm stage. 
Films were made by drawing cover glasses over the cut surface of the spleen, and 
then either dried in the air and stained with alcoholic solution of methyl blue, or, what 
we found much better, on Dr Muir's suggestion, fixed by a warm saturated solution of 
corrosive sublimate for half-an-hour, taken through successive alcohols, stained with 
Ehrlich's acid hsomatoxylin, and subsequently, in some instances, with alcoholic 
solution of eosine. The surplus hamiatoxylin was removed by washing in acid alcohol, 
and the films were cleared with clove oil before they were mounted in balsam. The 
blood films, after being dried in the air for not less than twenty-four hours, were stained 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 313 

with a saturated alcoholic solution of methyl blue, and sometimes also with a weak 
alcoholic solution of fuchsine ; they were washed in water, allowed to dry, and mounted 
in balsam. 

It is now my pleasant duty to express my thanks to those who have so kindly 
helped me in my research, more especially to Professor Rutherford, for the constant 
interest he has shown in my work, for many valuable suggestions, for much patient 
advice, and for the generous manner in which he placed at my disposal the resources of 
his laboratory ; also to Sir William Turner, to Professor Haycraft of Cardiff, to 
Dr Sims Woodhead of the Laboratory of the Conjoint Colleges, to Dr Carlier and 
Dr Muir of the University of Edinburgh, to Dr Raimes of York, and to Mr Gray, 
formerly of the Laboratory of the Royal College of Physicians in Edinburgh. 



314 DR A. J. WHITING ON THE 



BIBLIOGRAPHY. 

1. Muller, J., " Ueber die Struktur der eigcnthiimlichen korperchen in der Milz einiger pflanzenfressender 

Siiugethiere " (Arch. f. Anat. u. Physiol., p. 1, 1834). 

2. Id., Art. on the "Structure of the Spleen "(in Elements of Physiology, translated by W. Baly, M.D., 

vol. i. p. 567, 1838). 

3. Sanders, W. R, "On the Structure of the Spleen" (in Goodsir's Annals of Anat. and Physiol., vol. i. 

pp. 49-104, 1849). 

4. Kolliker, A., Art. on the " Structure of the Spleen " (in Manual of Human Histology, translated by 

Busk and Huxley, New Syd. Soc, vol. ii. p. 138, 1854). 

5. Remak, R., " Ueber runde Blutgerinnsel und liber pigmentkugelhaltige Zellen " (Midler's Arehiv, 

pp. 115-162, 1852). 

6. Virchow, M., Virchow's Arehiv, Bd. 4, and Brit, and For. Med. Chir. Review, vol. ix. p. 275, 1853. 

7. Huxley, T., " On the ultimate structure and relations of the Malpighian bodies of the Spleen and of the 

Tonsillar Follicles" (Quart. Jour. Micros. Sci., vol. ii. pp. 74-82, 1854). 

8. Billroth, T., " Beitriige zur vergleichenden Histologic der Milz " (Arch. f. Anat., Physiol., u. Wissench. 

Medicin, Muller, p. 88, 1857). 

9. Id., " Zur normalen und pathologischen Anatomie der menschlichen Milz " (Virchow's Arehiv, Bd. 20, 

pp. 409-425, 1861). 

10. Schweigger-Seidel, F., " Untersuchungen liber die Milz " (Virchow's Arehiv, vol. xxiii. p. 526, 1862, 

and vol. xxvii. pp. 460-504, 1863). 

11. Muller, W., Ueber den feineren Bau der Milz, Leipzig, 1865. 

12. Id., Art. on the " Spleen" (in Strieker's Manual of Human and Comparative Histology, New Syd. Soc, 

vol. i. pp. 348-364, 1870). 

13. Ktber, E., " Ueber der Milz des Menschen und einiger Siiugethiere " (Arch. f. Mikros. Anat., Bd. 6, 

pp. 540-580, 1870). 

14. Fret, H., The Histology and Histochemistry of Man, trans, by A. E. J. Barker, pp. 426-440, 1874. 

15. Id., The Microscope and Microscopic Technology, 4th Ed., trans, by R. Cutter, M.D., pp. 481-484, 1872. 

16. Klein, E., "Observations on the Structure of the Spleen" (Quart. Jour. Micros. Sci., N.S., vol. xv. 

p. 363, 1875). 

17. Id., Atlas of Histology, by Klein and Noble Smith, p. 423, 1880. 

18. Pouchet, G., "Des Terminaisons Vasculaires dans la Rate des Selaciens" (Journ. de V Anat. et de la 

Physiol, Tome xviii. pp. 498-502, 1882). 

19. Mobius, O., " Zellvermehrung in der Milz beim Erwachsenen " (Arch. f. Mikr. Anat, Bd. 24, pp. 342-345, 

1884). 

20. Kultsuhitzki, N., "Ueber die Structur der Milz," Charkow, 1882 (Jahresb. d. Anat. u. Physiol., Bd. 

12, p. 173, 1883). 

21. Stilling, H., " Fragmente zur Pathologie der Milz. Ueber progressive und regressive Metamorphosen der 

Follikel" (Virchow's Arehiv, Bd. 103, pp. 15-38, 1886). 

22. Robertson, R., " A contribution to Splenic Histology " (Jour. Anat. and Physiol., vol. xx. p. 509, 

1886). 

23. Arnold, J., " Ueber Kern und Zelltheilungen in der Milz " (Arch. f. Mikros. Anat., vol. xxxi. p. 541, 

1888). 

24. Denys, J., "Sur la Fragmentation Indirecte" (La Cellule, Tome v. p. 159, 1889). 

25. Schafer, E. A., Proc. Physiol. Soc, pp. ix. x. (Jour, of Physiol., vol. ix. Nos. 4 and 5, 1890). 

26. Bannwartu, " Untersuchungen iiber die Milz ; Die Milz der Katze " (Arch. f. Mikros. Anat., Bd. 33, 

pp. 345-446, 1891). 

27. Ukmak, li., " Ueber vielkernige Zellen der Leber" (Midler's Arehiv, pp. 99-102, 1854). 

28. Neumann, E., " Neiie Beitragc zur Kenntniss der Blutbildung" (Arch. d. Heilkunde, Bd. 15, pp. 441-476, 

1874). 

29. Id., " Ueber Blutregeneration und Blutbildung" (Zeitschr. f. /din. Med., Bd. 3, p. 411, 1881). 



COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 315 

30. Bizzozero and Salvioli, " Experimentale Untersuchungen iiber die lienale Haniatopoesis " (Moleschott's 

Untersuehungen, Bd. 12, pp. 595-610, 1881). 

31. Bizzozero, J., "Ueber die Bildung der rothen Blutkorperchen " (Virchow's Archiv, Bd. 95, pp. 26-44, 

1884). 

32. Hayem, G., Du Sang etde ses Alterations Anatomiques (Paris, 1889). 

33. Gibson, J. Lockhart, " The blood-forming organs and blood formation " (Jour. Anat. and Physiol, vol. 

xx., 1885). 

34. Schoney, L., " Ueber den Ossificationsprocess bei Vogeln und die Neubildung von rothen Blutkor- 

perchen an der Ossificationsgrenze " (Arch.f. Mikr. Anat., Bd. 12, p. 244, 1876). 
35 Schafer, E. A., " Note on the intracellular development of blood-corpuscles in Mammalia " (Proc. Roy. 
Soc, vol. xxii. p. 243, 1874). 

36. Creighton, C, " Illustrations of the Pathology of Sarcoma " (Jour. Anat. and Physiol., vol. xiv. p. 292, 

1879). 

37. Arndt, R., " Untersuchungen an der rothen Blutkorperchen der Wirbelthiere (Virchow's Archiv, Bd. 83, 

pp. 15-41, 1881). 

38. Foa and Salvioli, " Sull' origine dei globuli rossi del Sangue," Arch, per I. Scienze mediche, vol. iv. 

p. 1 (CentralMatt f. d. Medicin. Wissensch., p. 125, 1880). 

39. Howell, W. H., Observations upon the Occurrence, Structure, and Function of the Giant Cells of the 

Marrow (Jour, of Morphol, vol. iv. p. 117, 1891). 

40. Malassez, L., " Sur l'origine de la formation des globules rouges dans la moelle des os " (Arch, de 

Physiol., Tome ix. pp. 1-47, 1882). 

41. Gensch, H., " Die Blutbildung auf dem Dottersack bei Knochenfischen " (Arch. f. Mikr. Anat, Bd. 19, 

p. 144, 1881). 

42. Wissozky, N., " Ueber das Eosin als Reagens auf Hamoglobin und die Bildung von Blutgefassen und 

Blutkorperchen bei Saugethier und Hiihnerembryonen " (Arch. f. Mikr. Anat., Bd. 13, p. 479, 
1876). 

43. Bayerl, B., " Die Entstehung rother Blutkorperchen im Knorpel am Ossificationsrande " (Arch. f. 

Mikr. Anat., Bd. 23, p. 30, 1883). 

44. Osler, W., " Problems in the Physiology of the Blood-Corpuscles " (Brit. Med. Jour., pp. 807 and 862, 
1886). 

45. Ranvier, Traiie Technique d' 'Histologic, 1889. 

46. Kuborn, P. " Du Developpement des vaisseaux et du sang dans le foie de l'embryon " (Anatomisch. 
Anzeiger, p. 277, 1890). 

47. Muir, R., "Contributions to the Physiology and Pathology of the Blood" (Jour, of Anat. and Physiol., 
1891). 

48. Stricht, 0. Van der, " Le developpement du Sang dans le foie embryonnaire " (Archives de Biologie, Tome 
xi. pp. 19-113 1891). 



316 COMPARATIVE HISTOLOGY AND PHYSIOLOGY OF THE SPLEEN. 



DESCRIPTION OF FIGURES. 

Plate I. 

Fig. 1. Hilar sheath in spleen of cat x 50. 1. Muscular layer. 2. Connective tissue layer. 3. Artery. 
4. Vein. 5. Nerve. 

Fig. 2. Hilar sheath in spleen of hedgehog x 60. 1. Muscular layer. 2. Connective tissue layer. 3. Artery. 
4. Adenoid sheath. 5. Follicle. 

Fig. 3. Follicle in spleen of rook (y^th inch Beck, water-immersion). 1. Arteries. 2. Capillary. 3. Lym- 
phoid cells. 4. Large cells in follicle. 5. Large cells in pulp. 6. Peripheral muscular layer. 

Fig. 4. Follicle in spleen of hedgehog x 300. (Upper portion of fig. 2, more highly magnified.) 1. Artery. 
2. Hilar sheath. 3. Lymphoid cells of follicle. 4. Peripheral muscular layer continuous with 
hilar sheath. 5. Adenoid sheath. 6. Cells of pulp. 

Plate II. 

Fig. 5. Ellipsoid in spleen of ox (y^th inch Beck, water-immersion). 1. Axial vessel. 2. Ground substance 
with lymphoid cells. 3. Peripheral layer of spindle cells. 4. Microscopic trabeculse. 5. Cells 
of pulp. 

Fig. 6. Ellipsoid in spleen of dog x 350. 1. Entering artery. 2. Axial vessel. 3. Emergent vessels. 
4. Capillary channels. 5. Lymphoid cells in ground substance. 6. Surrounding blood-sinus. 
7. Cells of pulp. 

Fig. 7. Reticulum of pulp in spleen of dog x 350. 1 . Cells of reticulum. 2. Lymphoid cells. 3. Proto- 
plasmic corpuscles. 

Fig. 8. Reticulum of pulp in spleen of frog with cells containing pigment x 300. 

Fig. 9. Cells of pulp in spleen of tortoise (Zeiss, E.). 1. Giant cells. 2. Protoplasmic corpuscle. 3. Lym- 
phoid cells. 

Figs. 10 & 11. Giant cells and erythroblasts in pulp of spleen of young pig (Zeiss, E.). 

Fig. 12. Giant cell in pulp of spleen of puppy (Zeiss, E.). 1. Erythroblast apparently within giant cell. 
2. Erythroblasts around giant cell. 3. Lymphoid cells. 

Plate III. 

Fig. 13. Uninucleated vacuolated cell in pulp of spleen of half-grown rat (Zeiss, E.). 

Fig. 14. Uninucleated vacuolated cells in pulp of spleen of guinea-pig (Zeiss, E.). 

Fig. 15. Giant cell in spleen of an eight months' human foetus (Zeiss, E.). 1. Giant cell, with pyriform 
nuclei, vacuoles, and mouth-like openings. 2. Erythroblasts. 3. Lymphoid cells. 4. Red blood- 
corpuscles. 

Fig. 16. Cells of pulp in spleen of an eight months' human foetus (Zeiss, E.). 1. Venule. 2. Special 
multinucleated vacuolated cell. 3. Young giant cell. 4. Erythroblasts. 5. Red blood- 
corpuscles. 6. Spindle-shaped fibres, apparently muscular, in wall of vein, some cut obliquely, 
others transversely. 

Fig. 17. Special multinucleated vacuolated cell in same spleen, showing numerous empty vacuoles (Zeiss, E.). 

Fig. 18. Special cell in spleen of child, showing an erythroblast within a vacuole (Zeiss, E.). 

Figs. 19 & 20. Special cells in spleen of child (Zeiss, E.). 

Fig. 21. Giant cell in spleen of child (Zeiss, E.). 

Fig. 22. Giant cell with budding nucleus in spleen from case of leucocythsemia (Zeiss, E.). 

Fig. 23. Giant cell in spleen of anasmic dog (Zeiss, E.). 



Trans. Roy Soc. Edm 1 : Vol. XXXVII. 

Dr Whiting on the Comparative Histology of the Spleen — Plate 1. 




M'Fa.rlane ^Erslune. Lith r ? EdinT 



Trans. Roy Soc. Edm r , Vol. XXXVIII. 

D r Whiting on the Comparative Histology of the Spleen — Plate 11. 



Fii$. 5 




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Trans. Roy. Soc. EdmT, Vol. XXXVIII. 
Df Whiting on the Comparative Histology of the Spleen — Plate III. 




Fi<513. 




Fig. 14. 




Fi£.15. 





Fie. 17. 



Fig. 18. 



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Fig. 21. 





Fig. 22. 



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M'Farlane ^Erslune, Lith r ? Edin r 



( 317) 



IX. — Specific Gravities and Oceanic Circulation. By Alex. Buchan, M.A., LL.D. 

(With Maps.) 

In the report on Oceanic Circulation, based on the observations made on board H.M.S. 
" Challenger," and other observations, which was published in the beginning of 1895 as an 
Appendix in the Summary of Eesults, Second Part Challenger Reports, the specific 
gravities dealt with were all at the standard temperature of 60° Fahr., the standard 
density being that of distilled water at 39°'2 (4° C). By this method of treatment the 
question of the salinity or saltness of the water is approximately stated, unquestionably 
one of the most important questions affecting the physics of the ocean. But the move- 
ment of the water, or oceanic circulation, as resulting from different densities, can only 
be represented by stating, not the specific gravity reduced to the uniform temperature of 
60°, but the specific gravity at the observed temperature at all points in the ocean at 
which observations are made. In this paper these specific gravities are viewed in their 
relations to the circulation of the waters of the ocean. 

In the Challenger Eeport every effort was made to secure that the maps of mean 
temperature and mean specific gravity of the surface of the ocean were constructed from 
annual means, since maps thus constructed are altogether indispensable in any discussion 
of oceanic circulation. This discussion therefore proceeds from data, representing on a 
map of the earth the mean annual specific gravity of the surface waters at the mean 
annual temperatures of the surface. Map 1 represents such a map, which has been con- 
structed in this way : — A table of mean annual temperature for every 10° of longitude 
and every 5° of latitude was constructed from the map of surface temperature given in 
the Challenger Report, and a similar table of mean annual specific gravity at the 
temperature of 60°. * From these two tables another table was constructed, giving the 
mean specific gravity at the temperature of the surface for the same points of the ocean, 
numbering in all 640 points. The mean of these 640 specific gravities is T0252, 
allowance being made for the diminution, with latitude, of the areas of the " squares." 
Each of the specific gravities was then compared with this general average, the difference 
entered in its place on the map, and the lines of differences — 0-0010, - 0020, and 0"0030, 
&c, above and below the average — were thereafter drawn on the map.t 

None of the observations on board the " Vitiaz " were made at greater depths than 
800 metres or 437 fathoms ; and those on board the " Gazelle " only at the surface, at 
depths of 50 and 100 fathoms, and at the bottom of the ocean. Hence the observa- 
tions on board these ships are unfortunately seriously defective as aids in discussing the 
problem of oceanic circulation. A considerable number of observations, such as those 

* Report, Maps 1 and 2. 

t For sources of information from which the specific gravities have oeen obtained, see Appendix, p. 342. 
VOL. XXXVIII. PART II. (XO. 9). 2 U 



IU8 DR ALEXANDER BUCHAN ON 

observed on board the " No vara," could not be utilised, since the temperature of the sub- 
surface water was not recorded along with the specific gravities. 

An. examination of the observations which are available shows that the number is 
sufficient to represent important sections of the ocean only at depths of 100, 200, 300, 
400, 800, and from 1500 fathoms to the bottom, Maps 2 to 8 ; the number at other 
depths are al together insufficient to represent any considerable portion of the ocean which 
could cast additional light on oceanic circulation. Thus, at 500 fathoms there are only 
11 observations; only 6 at 600 fathoms; and even at 1000 fathoms the number is 
only 7. Hence it is impossible yet to attempt to represent the specific gravity of the 
ocean at any other depths than those dealt with, even over comparatively limited 
areas. 

Since in constructing Map 1 the data employed are fairly good annual means, the 
mean specific gravity of the surface of the ocean may be represented by coloured shadings 
of red and blue, according as above or below the mean specific gravity of all the oceans 
taken together, or 1"0252. But, as regards all the other maps, the observations are too 
few, and, with reference to the different expeditions, are necessarily disposed in lines and 
not in a scattered manner over the different oceans traversed. It has therefore been 
judged expedient to represent the results not by lines, but only the actual observations 
themselves. These are given in the form of differences from the simple mean of the whole 
observations made at the depth represented by each map. When the differences are 
above this mean the figures are red, but when under it they are blue. Thus, at 100 
fathoms the mean of all the observations is 1*0261 ; if, then, 14 in red ink is entered on 
the map at any point, the specific gravity there is 1*0275 ; but if it is entered as 17 in 
black ink, then it is 1*0244. In this way the maps represent the actual state of our 
knowledge at present ; and what is of the utmost importance, they show us in a most 
impressive manner the enormous tracts of the ocean for which we have absolutely no 
observations— in other words, of which we possess no real knowledge. 

The following are the more important of these enormous blanks in the ocean at 
depths of 100 fathoms and lower : — The whole of the North Atlantic between long. 10° 
and GO °W. to the north of lat. 40° N. is not represented by a single observation — a state 
of matters not creditable to this country. For some considerable distance to the east of 
the United States, the whole of the Gulf of Mexico, the Caribbean Sea, and an immense 
region to the south-east, from lat. 20° N. to South America, as far to eastward as 
long. 30° W. — a region whose importance in this inquiry it is impossible to over-estimate 
— are enormous blanks, not creditable to the Governments of the United States, Great 
Britain, and Brazil. If we except the observations of the " Gazelle " at 100 fathoms and 
at the bottom, and Admiral Makaroff's down to 437 fathoms, the whole of the Indian 
Ocean presents an unrelieved blank, an ocean so very important in the inquiry, seeing 
( li.it it is a closed ocean north of lat. 25° N. The Pacific Ocean is unrepresented 
to the north of lat. 40° N. and east of long. 170° E., and also to the east of a line 
drawn from about lat. 35° N. and long. 155° W. to lat. 30° S. and long. 130° W. Except 



SPECIFIC GRAVITIES AND OCEANIC CIRCULATION. 



319 



the " Challenger " observations and a few made by the " Gazelle " near South America, 
the Great Southern Ocean is without observations to the south of about lat. 45° S. ; and, 
as regards this region, no other part of the ocean of equal influence and importance can 
be named as ruling oceanic circulation. 

The following is a list of the maps * : — 

Map 1. — Mean Annual Specific Gravity of the Surface of the Ocean at Tempera- 
ture of Observation. 
Map 2. — Specific Gravity at Observed Temperature at depth of 100 fathoms. 



Map 3. 
Map 4. 
Map 5. 
Map 6. 
Map 7. 



Do. 
Do. 
Do. 
Do. 
Do. 



do. 
do. 
do. 
do. 
do. 



do. 


200 fathoms. 


do. 


300 fathoms. 


do. 


400 fathoms. 


do. 


800 fathoms. 



from depth of 1500 
fathoms, to the bottom. 



60° 
39-2 



at depth of 100 fathoms. 

depth of 1500 fathoms to 



Map 8. — Specific Gravity of the Ocean S 

Map 9.— Do. do. 

the bottom. 
The following table shows the mean specific gravity of the ocean deduced, as above 
described, from all available observations at the various selected depths ; first, reduced 
to the uniform temperature of 60° ; and, second, to the observed temperatures of the 
observations. In calculating these averages, the observations made in " closed areas " 
were not used ; the observations are, however, entered on the maps. 





At 60°. 


At Observed 




Temperatures. 


Mean specific at surface, 


1-0262 


1-0252 


,, 100 fathoms, 


1-0260 


1-0261 


200 „ 


1-0258 


1-0268 


300 „ 


1-0257 


1-0271 


400 „ 


1-0256 


1-0273 


800 „ 


1-0256 


1-0276 


1500+ „ 


1-0258 


1-0279 


2000+ „ 


1-0258 


1-0280 



Since the first column, which shows the specific gravities reduced to the uniform 
temperature of 60°, may be regarded as giving the approximate salinities t of the ocean 
at the different depths, it is seen that the mean salinity of the ocean is the maximum at 
the surface,— that it steadily diminishes from 1-0262 to T0256 from the surface to 800 

* Maps showing specific gravity at ( S— J were also constructed for depths of 200, 300, 400, and 800 fathoms, 

which are not produced with this Paper, but are referred to in the text. 

t In this paper the term salinity will, for convenience, be employed to represent the specific gravity at 60'. 



320 DR ALEXANDER BUCHAN ON 

fathoms at least; but that at 1500, 2000, and greater depths, it increases to 10258. 
With reference to the increased salinities of the ocean at depth of 1500 fathoms and 
greater depths, it is suggested in the Challenger Report under the heading " The Southern 
Ocean," pp. 36-38, that it probably has its origin in the relatively high salinity of the 
surface water of the south portions of the Atlantic, Indian, and Pacific Oceans. These 
surface waters are driven southwards by the strong west-north-westerly winds till, 
reaching the region characterised by heavy rainfall and extensive ice-melting, they sink 
to great depths, bearing their high salinity with them. Future observations, which may 
more adequately represent the temperature and salinity of the great Southern Ocean 
through its depths can alone teach us the true state of the circulation of the waters of 
this part of the ocean. 

On the other hand, the actual specific gravities at the observed temperatures of the 
different depths, which alone determine movement, are essentially different from the 
above. Here there is a steady increase of specific gravity, with depth from 1*0252 at 
the surface to 1*0280 at 2000 fathoms and greater depths. It follows from what has 
been said that this increase of specific gravity with depth is wholly occasioned by the 
decrease of temperature down to at least 800 fathoms, as shown by the maps of sea 
temperature given with the Challenger Report on Oceanic Circulation. But, at depths of 
1500 and under, the increasing specific gravity is due both to the slowly diminishing 
temperature and also to the actual increase of the salinity of the ocean at these great 
depths. It cannot be doubted that the increased salinity at great depths, where the 
differences of temperature with depth are very small, is an important factor concerned in 
the distribution over the bed of the ocean of low temperatures, chiefly from the 
Antarctic and sub-Antarctic regions, and in a less degree, the Arctic and sub-Arctic 
regions of the globe. 

The distribution of the different degrees of salinity of the ocean over its surface is 
determined by the prevailing winds taken in connection with their relative dryness, the 
upwelling from lower depths which occurs chiefly along those coasts where the prevail- 
ing winds blow from the land seawards, and the amount of the rainfall. 

The prevailing winds over the ocean may be best studied in detail by referring to the 
Challenger Report on Atmospheric Circulation, pp. 48-69, and the Maps 27-52 of that 
Report, which show the isobaric lines and prevailing winds of the globe for the months 
and the year. In these maps the general movement of the atmosphere over the different 
oceans through the months of the year is clearly shown. The outstanding features of 
the circulation of the atmosphere bearing on this discussion will be conveniently shown 
by a somewhat detailed examination of the prevailing winds in January and July. 

Prevailing Winds in January. — In the North Atlantic, north of lat. 35° N, atmos- 
pheric circulation is ruled by the low pressure in the neighbourhood of Iceland taken in 
connection with the systems of high pressure over Eurasia on the one hand and North 
America on the other. From this distribution of the mass of the earth's atmosphere it 



SPECIFIC GRAVITIES AND OCEANIC CIRCULATION. 321 

inevitably follows that over the eastern parts of America the prevailing winds are 
north-westerly, and over western Europe south-westerly. Hence, the prevailing winds 
at this season blow the surface waters of the ocean from the American coasts and West 
Indies across the Atlantic, then northward over its eastern side, and thereafter round the 
north of Norway and along the north coasts of Siberia. This state of things results, as 
regards Europe, in the setting in of a strong ocean current, bringing the waters of 
warmer latitudes to its western shores ; and, on the other hand, as regards America, the 
draining away from its shores of its warmer surface waters ; and as this water is necessarily 
replaced by the upwelling from greater depths, it is therefore of a lower temperature 
than that removed by the surface currents. 

Similarly, the wind system of the North Pacific is ruled by the low pressure in the 
north of that ocean, resulting in north-westerly winds in the east of Asia and south- 
westerly and southerly winds in the west of North America. The great dryness and 
extremely low temperature of these north-westerly winds have the effect of lowering 
to a still greater degree the temperature of the North Pacific Ocean. 

In the southern hemisphere, south of lat. 35° S., there occur no circumscribed regions 
of low pressure, but, instead, a broad ring, in width about 30° of latitude, of very low 
pressure, passes completely round the globe, falling to a mean pressure of about 29'000 
inches near latitude 63° S. Over this broad space of low pressure the prevailing winds 
are strong and approximately westerly or north-westerly all the year round. These 
strong north-westers, which blow in upon the Southern Ocean by the surface currents 
they originate and maintain, inconceivably enormous volumes of water from lower 
latitudes, and these waters moreover of a comparatively high temperature and salinity. 
These warm and specifically heavy waters, on advancing in their passage southward to 
those parts of the Southern Ocean where the surface temperature and salinity are low 
owing to the heavy rainfall, icebergs and melted snow, sink to greater depths and thus 
become overlaid by the specifically light waters of the Antarctic region, as suggested by 
Dr Murray.* A marked feature of the waters of the Southern Ocean is the interdigita- 
tion of currents differing widely from each other both in temperature and salinity, the 
colder of these currents having their origin, no doubt, in the numerous icebergs of these 
regions. An important part played by these vast currents of warm and specifically 
heavy water, is to mitigate very materially the cold of Antarctic regions, particularly 
at great depths, and thus confine the ice-clad area to its present limits. 

At this time of the year restricted systems of low atmospheric pressure are not to be 
seen over the ocean, but over the land of the Southern Hemisphere. Of such systems 
there are these three : — In Australia, South Africa, and South America. The best defined 
of these systems is Australia, where on all coasts winds blow from the sea upon the land, 
under whose influence the surface currents of the ocean are directed towards the land. 

Prevailing Winds in July. — -In this season the geographical distribution of pressure is 

* " The Renewal of Antarctic Exploration." By John Murray, Ph.D., LL.D., of the Challenger Expedition (Geogr 
Journ., vol. iii. p. 18, 1894.) 



322 DR ALEXANDER BUCHAN ON 

exactly the reverse in Australia of what obtains in January. Everywhere it increases on 
advancing from the coast into inland regions. The lowest pressure, about 30*000 inches, 
occurs near the north coast, and the highest 30 '180 inches, over the basin of the Murray 
Eiver and its affluents. From this region the diminution of pressure continues uninter- 
ruptedly northward as far as the summer low pressure system of Asia. Hence, the prevailing 
winds of Australia are essentially an outflow from the high pressure region of the interior 
towards the lower pressures of the coasts, particularly the north coast ; and the winds 
are therefore S.E. on the north coast, S.W. at Brisbane, W.N.W. at Sydney, N. at Mel- 
bourne, and N.E. at Adelaide. 

The high pressure of the south of Australia is continued westwards in the same 
latitudes through the Indian Ocean. From these latitudes pressure falls continuously 
northwards to the low pressure area in Asia ; and, as the inevitable consequence 
of that diminution of pressure, southerly winds sweep across that ocean home into Asia. 
Where they reach the coast after having traversed a great extent of ocean, such as the 
coasts of India and Burmah, they precipitate a very heavy rainfall, which, from the serious 
lowering of the specific gravity thus occasioned, has a most retarding effect on the down- 
ward circulation of the ocean there. On the other hand, on the northern and western 
division of the Arabian Sea the rainfall is excessively small, since the winds there have 
traversed but a small breadth of the ocean ; and, consequently, from the dryness of these 
winds the salinity is much increased, and the vertical circulation becomes thereby greatly 
accelerated. 

Similarly, as pressure diminishes from about lat. 25° S. in the Pacific uninterruptedly 
to the low pressure of Asia, the prevailing summer winds on the south-eastern coasts of 
Asia, after having traversed a wide extent of ocean, pour a very heavy rainfall on these 
coasts and outlying islands, thus very greatly lowering the specific gravity of the surface 
during these months. 

The summer winds of Europe are determined by the high pressure of the Atlantic 
in its relation to the low pressure systems of Asia and Africa at this time of the year. 
On the coasts of Spain and North- West Africa the prevailing winds are northerly ; farther 
to the north, on the coasts of France and the British Islands, south-westerly ; and on the 
coasts of Norway westerly and north-westerly. The curving of the winds round the anti- 
cyclonic region of the North Atlantic, from N.E. off the coast of Africa to E. and S.E., 
as they near and pass the region of the West Indies, to S. and finally S.W. off the Eastern 
States of America, has all-important bearings on the circulation of the waters of this 
ocean. 

The centre of lowest pressure in North America is over the States about Utah, from 
which pressure rises all round, but chiefly to the south-east and west. In accordance 
with this arrangement of the pressure, the winds blow from the Gulf of Mexico home to 
the coasts of the States as southerly winds. On the other hand, the winds on the coasts 
of the Pacific States are N. and N.W. as far north as Vancouver, but over that island 
and the coasts to northward they are S.W. 



SPECIFIC GRAVITIES AND OCEANIC CIRCULATION. 323 

From lat. 30° to 63° S., as already explained, pressure diminishes uninterruptedly 
from 30'150 inches to 29*000 inches over a broad ring going round the whole globe 
during all seasons of the year. Now, over the whole of this vast space, westerly and 
north-westerly winds sweep as strong winds, subject to little, if any, variation with 
season. From the enormous quantities of warm water they impel before them into the 
Southern Ocean they may well be considered as playing the most conspicuous part of 
all the prevailing winds in the circulation of the waters of the ocean. 

As regards the salinity of the surface of the ocean, it is seen (Challenger Report, Map 
1) that the broad result is a high salinity in tropical and sub-tropical regions, where 
temperature and evaporation are high, and where the rainfall is small ; and a low salinity, 
where temperature or evaporation are low and the rainfall large. 

In the anti-cyclonic regions of the ocean salinity is large, since out of these regions 
winds blow in all directions, and the drain thereby caused being compensated by vast 
descending currents of very dry air, evaporation is necessarily large, thus occasioning a 
high salinity. Of this the anti-cyclonic region of the North Atlantic, which embraces the 
Sargasso Sea, is a good illustration. 

As already explained, the prevailing winds of the North Atlantic do not blow home 
to the eastern coasts of the United States, the prevailing winds there being south- 
westerly, and, consequently, the higher salinity is at some distance seaward from the 
coast. But, to the south of lat. 40° N., the prevailing winds become more westerly as 
they advance in their easterly course, and as they near the north-western coast of Africa 
become north-westerly and then northerly ; consequently, they blow home to the coast 
of the north-west of Africa, and there we find the higher salinities close on the 
coast. 

In the South Atlantic the south-east trades blow home to the coast from Cape St. 
Roque to the estuary of the La Plata in a manner more direct and unimpeded than any 
other part of the globe can show ; and, consequently, it is off this coast where the highest 
salinities are anywhere found. For a considerable portion of the year the winds of 
Western Australia are from the west, blowing out of the anti-cyclonic region of the 
Indian Ocean. On this coast also a higher salinity prevails close inshore. From- 
Australia to South America the salinitv is also high. 

The volume and strength of the oceanic current, generated and maintained by the 
prevailing winds of the North Atlantic, is impressively manifested by the high latitude, 
about lat 74° N., reached by the surface salinity of the ocean, 1*0260 and upwards. In 
the North Pacific the highest latitude reached by this degree of salinity is lat. 36° N. 
In other words, this salinity is pushed 38° of latitude farther northward in the Atlantic 
than in the Pacific. 

On the other hand, in the tropical parts of the Pacific is an extensive region, 
stretching in length from Panama to long. 170° E., and in breadth from 15° to 20° 
of latitude, over which the degree of salinity is a little less than 1*0260. This 
is a region characterised by light trade winds and extensive upwelling of the water 



324 BR ALEXANDER BUCHAN ON 

from lower depths. The salinity is also under 1'0260 in the Gulf of Guinea and 
East Africa, from about lat. 1° N. to lat. 10° S., these comparatively low salinities 
being in all probability occasioned by the heavy rainfall characteristic of both these 
coasts. 

But by far the most remarkable region of low salinity, both as regards extent and 
the very low degree to which it is reduced, is that which extends from India, through the 
East India Islands, to long. 143° E. Further, it extends across the equator to lat. 9° S., 
and over no inconsiderable breadth the salinity is less than 1"0250. It is to this exten- 
sive region of comparatively brackish water which the prevailing winds drive first north- 
wards and then eastwards across the Pacific that we must look for an explanation of 
the extraordinarily low salinity of the North Pacific, taken as a whole and at all depths, 
brought about by this surface current. Indeed, the salinity of this ocean may be 
regarded as abnormally low compared with the other oceans, but more particularly with 
the North Atlantic. 

Another consideration which has the most vital bearings on the question of oceanic 
circulation is the position of the line of lowest mean atmospheric pressure in inter-tropical 
regions, seeing that it is towards this line that the prevailing winds and their attending 
ocean currents flow. 

As regards the Atlantic, through all its breadth and in all seasons, this critical line of 
lowest pressure is situated to the north of the equator. It follows, therefore, that since 
the surface currents of the South Atlantic, generated and maintained by the south-east 
trades, cross the equator, they convey a high temperature and a high salinity into a 
hemisphere other than that in which they have their origin. The remarkable salinity of 
the North Atlantic, which is markedly higher than that of any other ocean, has its 
explanation in the enormous overflowings into it by the surface currents of the South 
Atlantic, together with the equally remarkable contributions to the salinity at the 
greater depths from the Mediterranean Sea to be afterwards referred to. 

Quite different is it with regard to the Pacific Ocean, where, in its western division, 
the line of lowest atmospheric pressure is for eight months of the year to the south of 
the equator, where, accordingly, northerly winds, with their accompanying ocean 
currents, cross the equator to lat. 15° S., as shown by the current charts in course of 
preparation by the Meteorological Council. 

The result is that the temperature and salinity conditions of these two great oceans 
are reversed. In the Atlantic the highest temperature and salinity are north of the 
equator, but in the Pacific to the south of it ; and the lowest temperature and salinity 
are in the Atlantic, south of the equator, but in the Pacific to the north of it. 

Another important result of the geographical distribution of atmospheric pressure in 
the Atlantic and Pacific Oceans respectively is that in the Atlantic the north and the 
south trades are stronger and more persistent than those of the Pacific, and the inter- 
space between them characterised by calm and light variable winds is therefore much 
narrower in the Atlantic than in the Pacific. From this it follows that the region of 



SPECIFIC GRAVITIES AND OCEANIC CIRCULATION. 325 

higher surface temperature and of lower salinity in the Atlantic is comparatively much 
contracted in width ; whereas in the Pacific the breadths occupied are several times 
greater. It is interesting to note that the lower salinity in the central Atlantic, between 
the high salinity to the north and south, marks with great distinctness the region between 
the two trade winds